Unexpected Shutdown

Has the user referred to the link in Top of this page ?

Incase it was overlooked there is is again and may provide some insights as to why this issue is occurring

If your Mac restarted because of a problem - Apple Support

Should the information above is not enough to isolate where the issue is occurring >>

Suggest the User start with Points 1 to 4 and then Test

Still having issues, move onto Steps 5 and 6 and Test Again

Still no resolve - move onto Step 7 and follow instructions therein 

1 - Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

2 - Safe Mode will also eliminate Third Party Software, extensions and drivers from loading. It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 

3 - Does the issue present in this mode ?

4 - Sometimes a Safe Boot followed by a Normal Boot will just put things right.

5 - If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

6 - If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

7 - Download the Application Etrecheck directly from the Developer.

This is a Diagnostic Tool that makes no changes to the computer.

It makes a coherent and readable inventory of both the Hardware and Software used on the computer 

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

I have been having this issue as well. My iMac ONLY crashes when it's in sleep mode.

Today, I updated to 13.4, then left the house. Chrome was open, other than that, no other apps were running except whatever may have been running in the background. FWIW, before updating, I disabled a bunch of background apps that don't need to truly run at login. Still happened today.

I'm not 100 percent sure when it started, but I believe around one of the versions of Catalina. It was only occasionally, but it's become more frequent now.

One thing I'm trying (because believe it or not, I just now thought about the fact that it's only when it's in sleep mode) is to actually NOT have it go to sleep and only use the screen saver. We'll see how that goes.

24 hours - no sleep mode, no crashes.

Before that - 2 times in one day.