Update: Currently, things are holding steady and stable. My first suggestion to others with the same issue on iMacs is to disable the HD sleep option (and possibly enable to "Prevent computer form sleeping" option) in power saver settings. I'd obviously not suggest that as a permanent solution on a macbook but, it stopped the random crashes for me. I posted more details in my own thread about it: https://discussions.apple.com/thread/253010697
If that doesn't change anything and you still get what appear to be random crashes after a certain amount of time, I'd probably start logging CPU and GPU temps to see if they're climbing too high then causing the crash. You don't need 3rd party tools for that, you can just do something like this.
sudo ls && while true; do echo "\r\n\r\n\r\n\r\n======================================================\r\n$(date)\r\n======================================================" >> ~/Desktop/temp.log; sudo powermetrics --samplers smc -i1 -n1|grep -Ei "(thermal|temperature)" >> ~/Desktop/temp.log; sleep 5; done &
You'll have to be a sudo user to run it. It will run an infinite loop in the background and, every 5 seconds, spit out the CPU and GPU temps and timestamp to a file called temps.log on your desktop. The file will be there post-crash/reboot so you can see what the temperatures looked like leading up to the event.
Note that the process running the temp monitoring loop is only running as long as you're logged in. If you log out, reboot or the machine crashes, you'll have to run the command again to kick it off.
