iPhone 7 microphone and overheating issues after iOS 15.8 update

Let’s define “overheating”. If a device overheats it shuts down so it can’t be used, and displays a message saying it must cool down before it can be turned on, and it will probably be unusable for an hour or so. If you are seeing this it is a hardware problem and you should contact Apple support: 

• Click on “Support” at the top of this page
• Go to Contact Official Apple Support

Note that both of the above have options to receive a callback or chat

If you are not seeing this your phone has not overheated. However, if you fast charge your iPhone it may get very warm, and may pause charging at 80% and display a message saying that charging has paused, and will resume when the phone cools down. This is NOT overheating, and is normal when fast charging. It also won’t prevent you from using any app you have on your phone.

If you have just updated allow a couple of days for iOS to complete its “housekeeping"

Some apps that use a lot of energy or that use cellular data rather than Wi-Fi can cause the phone to run warmer. Worst offenders are Facebook, Instagram, TikTok, Snapchat, interactive games, watching streaming videos, and the Camera app. And having VPN installed, whether using it or not, can also consume a lot of energy.

All of these are manifestations of the 2nd Law of Thermodynamics.