Mac Pro (2010) random shutdown

[wulai]

My Mac Pro (2010, 2.4 macOS10.12.2) has randomly shutdown. When I reboot, there wasn't a dialog box saying that the computer shutdown unexpectedly, nor was there's a dialog to ask if I want to reopen applications or send a report to Apple. I can't figure out what's causing it. so I'm not sure what to check.

I have a about PSU posts
https://forums.macrumors.com/threads/mac-pro-5-1-2010-psu-squealing.2113483/#post-25968514
Help is greatly appreciated

 

[ActionableMango]

Does it shut down instantly, as if the power was cut?

This plus the squealing noise makes me think your PSU is going bad.

Also, it's a stretch, but maybe the AC power in that circuit is wonky.