Macbook wakes up and powers on by itself during sleep or shutdown

Run the third party app EtreCheck and post the complete report here so we can examine it for possible clues. More than likely you have some third party software installed which is causing problems. Other possibilities is file syncing to the cloud.

How to use the Add Text Feature When Posting an EtreCheck Report - Apple Community

Try selecting the Sleep option from the Apple menu. Before you do though, press the Caps Lock key so you when the Caps Lock LED goes out, then you know the laptop went to sleep. Closing the display clamshell lid does not guarantee the laptop will sleep (software may not allow it, or the Lid Angle Sensor may not be bad).

Plug in the laptop whenever you can do so to keep your battery charged. You can also select "Shutdown" from the Apple menu to completely power off the laptop.

Keep in mind that pressing any key or even touching the Trackpad can wake up or power on the laptop. Connecting or disconnecting any external devices can also wake up or power on the laptop. So disconnect them before initiating sleep or power off.

You can use the following Terminal command to see the sleep & wake & start/power on events for the current day:

pmset  -g  log  |  grep -iE 'Sleep  |Wake  |Start  ' | grep  -E  "^$(date  "+%F")"

If you want to see the sleep & wake & start/power events for the overnight hours when you put the laptop to sleep the night before, you can use this command (it will include all events for both days, not just for sleeping the laptop at night):

pmset  -g  log  |  grep -iE 'Sleep  |Wake  |Start  ' | grep  -E  "^$(date  "+%F")|^$(date -v -1d "+%F")"

You need to copy & paste the commands since there is very critical spacing involved or it will fail or deliver incorrect results.

The output of the commands will show the battery charge level at each event, and will provide the reason for the sleep & wake events although many of them may be cryptic. There may be a lot of entries shown since Macs tend to wake & sleep a lot overnight.

Edit: You can also try running the Apple Diagnostics to see if any hardware issues are detected. A passing diagnostic is meaningless since it rarely detects actual hardware issues, but it never hurts to try because if an issue is detected, then you do have a hardware problem.

The computer has other important issues outside of the Wake and Sleep issue  

Low disk space - This computer is running low on free hard drive space.

APPLE SSD AP0256Z 251.00 GB (Solid State - TRIM: Yes) 

Size: 245.11 GB >> Free: 43.90 GB >>  Available: 70.96 GB

The general rule is to keep about 15 % to about 20 % the the 245 GB Drive Capacity as Empty Space

Some even suggest about 100 GB of Empty Space

From another contributor @etresoft regarding Free Space and Available Space 

Free vs available disk space huge differe… - Apple Community

Quote >>  “ The "available" storage is the amount of used storage that the operating system could automatically delete if it felt that it was really necessary. The "free" storage is the amount that you can actually use for something.

There are system processes that run in the background and automatically delete some of the "available" storage and convert it to "free". If you completely run out of storage, then those system processes will try a little harder. When you "delete" files you are just hinting to the operating system that you don't need those files anymore. The operating system will eventually remove them, but on its own schedule.

Certain tools will allow you to force the issue and manually clean up some of this storage and manually delete local snapshots. But that is only temporary. "  << End Quote 

Purgeable Space is controlled by the Operating System and not the user 

https://support.apple.com/en-ca/guide/disk-utility/dskutl1005/mac

Verify some of your settings tucked away in Battery / power Options...

Battery>Options

Settings > Privacy & Security > Analytics & Improvements:

Further from the Terminal for some insight:

pmset -g log|grep -e " Sleep  " -e " Wake  "

got booted out...

here is Apple Support ref

If your Mac sleeps or wakes unexpectedly - Apple Support

no resolve with power settings...

I also might suspect software bug, or a faulty peripheral device

To be proactive you can file a bug report / submit your Apple Feedback here: Product Feedback - Apple

Call Customer Support (800) MY–APPLE (800–692–7753)

or on line https://getsupport.apple.com/

Outside the USA—Contact Apple for support and service by phone

See a list of Apple phone numbers around the world.

Contact Apple Support - Apple Support

You are using 8.7GB of Swap which is getting to be a lot and indicates your workloads may be too much for the 8GB of memory in your Mac. It is a shame Apple keeps selling under spec'd systems like this since 8GB should not even be an option these days.....16GB of memory should be the bare minimum no matter how a computer is to be used.

Is your Logitech software completely up to date? And is it compatible with macOS 26.2? I have been seeing a lot of users reporting issues with the Logitech software causing problems as Logitech is a bit behind on compatibility with recent macOS update patches. Even if you have the mouse disconnected, this software could still be misbehaving if it is not fully compatible with the current patch level of macOS.

IvKate wrote:

• if the lid is closed, the screens stay off, but the mac periodically plays a system sound similar to power being connected or disconnected

• if the mac is fully shut down, it can turn itself on after 15–30 minutes and play the normal startup sound

no keyboard, mouse, trackpad or other input devices are being used at the moment of wake.

Re-reading your original post, this stood out to me today. If the sound is actually due to the power adapter connection sound, then it would indicate a hardware issue of some sort. Is the power adapter connected directly to this laptop? If not, then that could be a problem. Also, try connecting the power adapter to the other USB-C port to see if that makes any difference. It could also be a bad Logic Board, or possibly a battery. I have seen one of the MBPros have power & charging issues, but don't recall the exact model at this time (it was one with MagSafe3 though).

Did you run the Apple Diagnostics with the Power Adapter connected? What was the result?

Also, did you try using the "pmset" command(s) I gave you previously to see why the laptop is powering on by itself (or Waking up)? You can modify the filter to only use the "Start " item to show you the time & reasons for the system powering on which can reduce the amount of information displayed like this (I removed two of the filters so only power on (aka "Start ") events if you want to focus on cold power on events or reboots:

pmset  -g  log  |  grep -iE 'Start  ' | grep  -E  "^$(date  "+%F")|^$(date -v -1d "+%F")"

You can also save the output to a text file so you can use any text editor to search for "Start " within the full report of the Sleep, Wake, and Start events. Notice the " | tee -a ~/Desktop/pmset-SleepWakeStart-log__2025-12-19.txt" at the end of the line which will save a log of the output while also displaying it on the screen. This will create the file on the Desktop, or if the file already exists it will append the data to the existing file (don't use any spaces in the file name or path...use a dash or underscore instead like I have done here).

pmset  -g  log  |  grep -iE 'Sleep  |Wake  |Start  ' | grep  -E  "^$(date  "+%F")|^$(date -v -1d "+%F")"  |  tee -a  ~/Desktop/pmset-SleepWakeStart-log__2025-12-19.txt

Some of the reasons shown for the Sleep, Wake, and Start/power on events may sometimes appear cryptic, but it may be possible to figure out the meaning using a system log....it can be tricky & time consuming. I find these commands are the easiest method to figure out what is occurring with macOS. Even @leroydouglas offered a similar suggestion, but mine reduces the clutter by restricting the events to the current day and/or the previous day depending on the command you choose to use.

Hopefully the events shown by these commands will be sufficient for identifying the source of the Wake & power on (aka Start) events. If not, then you will need to resort to the "log" command to look for what the system is doing at the time, but I hope you don't need to because that system log will have thousands of entries.....easily with hundreds of entries every second (perhaps even thousands). This is the only way I have found to figure out Sleep/Wake/PowerOn issues with macOS