Mac Shuts Down When Left Idle For a Few Minutes

Title tells the story, It's been happening on my MacBook Pro for many months. I go walk the dog and come back not to find my work where I left it, but either mac the start up screen OR with the "random software" interrupted shutdown" error. When I come in the office each day I have left work in progress I open up the the same error.

Now I'm getting the same issues on my work iMac at the office (8 months after I first added it to iCloud). So my guess is it is spread or caused via iCloud or maybe DropBox since those are the only two things connected to both.

Just like Tina below, I've contacted Apple Support - no help, PRAM, Disk utility, Reinstall OS, all to not avail. The only recommended thing I have not tried is to do a clean install. But now I'm convinced what ever is causing this will either still be there when I restore my files or if it works, it will come right back.

MY SOLUTION: all be it a poor one, is to intentionally leave a file open & unsaved in the forefront so it will block the shutdown with the save request.

This is no way to live with such an expensive product. APPLE Please Help! Apples approach seems to be 'give us all your money and deal with it.' Feels like my pleas would be better addressed by those Mac OS gurus out there. Anyone, Anyone, Buller... Find this thing and kill it.

I found this post from Tina Ven -Sounds Like the exact same thing (with some other issues added):

"Basically, the title says it all. Only one valid response. that didn't work. Following the suggestion , I'm reposting.

Whenever I leave the mac without any kind of interaction, it will either prompt me to ‘Put my Mac to Sleep’/‘Shut Down’, or it will just die on its own.

I’ve checked some other posts and threads on and off the site, but I can’t find one that fits my situation. I even tried bringing it to an Apple Store to have it examined just in case there was something wrong with the system or hardware. But it was working just fine when they checked it. So I thought that it was OK. But just right after I have brought it home and turned it on, it would still act weird as it has always been.

I’ve tried resetting PRAM and SMC, and even repairing permissions, everything that I could get ahold of, but unfortunately, none of those fixed the problem.

It all started just last week, when it stopped charging all of a sudden, and had first showed unusual behaviour. I can’t even update the OS since it won’t let me leave it alone even for a minute that I’m getting more and more frustrated.

Does anyone else have the same problem as me? If you do, how should I fix it? Or could you at least give me any suggestions?"