Catalina - iMac shuts down randomly

I had the same issue on a 2013 MBP, especially when on battery power. It was fine after installing catalina, but about a month later, it started randomly shutting down without any warning. It was happening about every ten minutes. I didn't find the root cause, but did find a workaround. I tried all sorts of things, including resetting SMC and nvram, and reinstalling MacOS. Then I tried creating a new user. When I logged in with that user, the problem didn't happen at all. Since I keep everything in iCloud, and OneDrive, it was easy to move everything over to the new user name, and now I just don't use the old user name, and no more shut downs.

I had a similar problem. In my case, my iMac started shutting down randomly when I moved (iMac and me) to a new office at work. Occasionally it would refuse to shutdown. I took it to the Apple Store, ran diagnostics, changed cables...the only solution was to turn it off and leave it unplugged overnight, then plug it in the next morning. Then, usually it would get through the workday without random shutdown.

Later, when I moved the iMac to my office at home, the iMac quit shutting down (after a couple of initial tantrums) and has been running fine since. I am guessing some sort of grounding problem in my office wiring.

My Mac started randomly shutting down and giving me an error message after installing Catalina. Often this is while I am using apps and working on a project (often only minutes into it when I have not saved... I lose all my work). Can this be fixed?

Yes Please @Applesupport can you please explain. My MacBook has done the same thing. No instances of it "working itself out" etc. Please explain why our Macs are randomly restarting for no explicable reason.

Since I upgraded my iMac (Late 2012) from Yosemite to Catalina on Feb 3 2020, when I shutdown, my screen first blinks black for a fraction of a second, then remains stuck for 1-2 minutes on my desktop picture, without my desktop items which were cleared upon the blink. It resumes proceeding by going to a restart without shutting down. Upon re-start, I am prompted "Your iMac did not shutdown properly... Do you want to re-open with the previous windows opened?" ( ...Bla bla bla...)

Any how, it might shut down well next time, whatever app is on or off. And it also might get stucked.

The problem is intermittent.

My computer is clean and was working perfectly on Yosemite.

I went through every fix up procedures provided by Apple after discussing the problem with them, competent staff.

Nothing helps or explains what is happening.

In my opinion, Catalina seems to be the problem of that shutdown problem.

Not only does my iMac 2017 randomly shut down and restart since Catalina, but it also WILL NOT SHUTDOWN frequently when I want it to. Only thing I can do is press the power button to shut it down. Usually I wait before updating to the latest OS. For whatever reason I didn't this tome and I am SO sorry. What a mess.

Mine appears to shut down when either on map software or photos. I thought maybe struggling with graphic intensive software. Thought it had gone away then returned after a couple of weeks. A real pain.

I have started having the same issue since I installed Catalina. Not sure what is going on. Also, it doesn't support some older programs I have

Apple Support needs to respond My Mac 2019 is also shutting down randomly maybe 1-2X a week.

i have same problem

Same issue since installing Catalina on 2013 MBP.