One of the machines I use regularly is a MacBook Pro (13- inch, 2020, four Thunderbolt 3 ports, 2GHz Quad-core Intel Core i5) running Catalina.
Periodically, if I leave it running (open, plugged in, not asleep or logged out) overnight, I come back to it and the machine is frozen. The arrow cursor is there, invariably near the upper left hand corner; but the screen is otherwise black, and nothing I do gets things moving again.
The question: What’s the best way to identify the culprit? Like most people here I run a lot of software…
If the only thing that works is to force a shutdown and restart it, then this sounds like a kernel panic (or something similar). Recent versions of macOS have made it harder to look through the console to figure out what went wrong, but that’s where you are likely to find the problem. Don’t ignore this — repeated problems like this could indicate hardware or software damage.
Howard Oakley has a good overview and has written some apps to make searching Console easier (Ulbow is your place to start):
My past troubles like this have been associated with early releases of Monterey and running virtual machines, such as VMWare and Docker containers. Doesn’t seem to be an issue now.