why does my macbook air keep restarting after 5 seconds of use ive had this problem for a month now

You mean like this

If your Mac starts up to a question mark

A folder with a flashing question mark means that your startup disk is no longer available or doesn't contain a working Mac operating system.

If the question mark appears only momentarily before your Mac starts up normally:

1. Reset NVRAM.
2. Make sure that your preferred startup disk is selected in Startup Disk preferences.

If the question mark persists, follow these steps:

1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.
2. Turn on your Mac and immediately press and hold Command (⌘) and R to start up from macOS Recovery.
3. While in macOS Recovery, use Disk Utility to repair your startup disk.
4. If Disk Utility found no errors or repaired all errors, reinstall macOS.
5. If you still need help, please contact Apple Support.

Is there an error message presented the next time it is restarted ?

If so, what exactly does it say verbatim ?

Has been happening for past two months - what actions have been taken to resolve this issue ?

If you boot into Safe Mode, does it still happen?