What is the reason for shutting down the computer?

Question

Iron

The computer turned itself off without any warnings or a blue screen (windows 7).
UPS was silent. Power outages excluded.
Tried to turn on the computer 2 times within 5 seconds. after shutdown. Didn't turn on. After 10 sec. managed to turn it on. Did not do anything.
I think maybe overheating? Although 31 degrees are determined on the case (Zalman U3), I don’t know what this temperature is really.

Answer 1

boot from LiveCD and test hardware, examine logs on Windows

Answer 2

Overheating is quite possible. Maybe overheating of the PSU, vidyahi be. Or the conduits are swollen.

Answer 3

Attach a photo of the body honored.