MacBook Pro experiencing random restarts and buggy behavior while running programs
&quot;Could someone please advise me on additional steps to take?&quot;

Check Activity Monitor (in /Applications/Utilities) to see if any processes are using excessive CPU% or Memory.

Make sure that all the software you use is up-to-date, and compatible with Big Sur.  (Very often, the cause of problems after upgrading the OS is because of old, incompatible software that is crashing or hanging -- particularly 'invisible' background processes.)

Create a new user account and test the problem there. If the problem goes away, you know that something in your old user account was causing it. It might be a Login Item, Launch Agent or other process that's programmed to launch, or settings/preferences that are incorrect or corrupt. Go back to the old user account and investigate. If the problem continues, then you know it's a System-level issue, not a user-level one.

Check the logs for messages about crashes, unexpected restarts, and other errors. https://support.apple.com/en-gb/guide/console/cnsl1012/mac


It's also possible that problems like unexpected restarts are caused by hardware problems, such as battery, power supply or logic board issues.