Computer shut down then restarts by itsself.

I'd do a search however this problem is so ambiguous everyone has different results and solutions.

Ever since 2 nights ago my computer has begun shutting it'self down suddenly and then rebooting a few seconds later. No error messages or anything. It's happened on some games but not others as far as i can tell but i don't think they are related.

Specs:
GPU Radeon HD 7870
CPU intel i5 3570k ivy bridge
RAM 2x 4gig (8gig)
Motherboard: Maximus V Gene
HDD 1Tb
PSU:OZC 700W

First thought was overheating but checking HWMonitor the temps seem to be within acceptable limits. The CPU was running at 60-70 degrees which is the most anomalous.

The event viewer gives me Event 41-Kernal power: The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.

Then 2 after that Event 89 Kernal-Power: First being ACPI thermal zone ACPI\ThermalZone\TZ00 has been enumerated.
_PSV = 0K
_TC1 = 0
_TC2 = 0
_TSP = 0ms
_AC0 = 358K
_AC1 = 328K
_AC2 = 273K
_AC3 = 273K
_AC4 = 273K
_AC5 = 0K
_AC6 = 0K
_AC7 = 0K
_AC8 = 0K
_AC9 = 0K
_CRT = 379K
_HOT = 0K
_PSL - see event data.

then
ACPI thermal zone ACPI\ThermalZone\TZ01 has been enumerated.
_PSV = 379K
_TC1 = 1
_TC2 = 5
_TSP = 1000ms
_AC0 = 0K
_AC1 = 0K
_AC2 = 0K
_AC3 = 0K
_AC4 = 0K
_AC5 = 0K
_AC6 = 0K
_AC7 = 0K
_AC8 = 0K
_AC9 = 0K
_CRT = 379K
_HOT = 0K
_PSL - see event data.

I'm thinking hardware wise must be overheating or dying but i've done a memtest86 for 2 passes and i put prime95 on for about 20 minutes.
I'm stumped.

Edit- Since it first happened i have reformatted my drive so i'm certain it's nothing software related.

 

What about your power supply?

 

Edited the main post. It's a 700W,
while i was monitoring this something from the ai suite did give a brief popup saying that VCORE was at 0.0v (I can't be certain of the value it only appeared for a second, but HWmonitor doesn't show anything below 0.8 as a minimum value.

 

Power supplies do fail. Two years ago, I had an Antec PSU with similar issues. I opened the case to clean it and it had several leaking capacitors. It served me well for several years but it's time had come.

 

Is there something i should look for to know if it's the reason? Theres about 10 different voltage sensors and i have no idea what values are what.

 

I had similar symptoms when my psu failed. It would randomly i.e. shut down, not turn on. Then after while refuse to turn on.

 

If I'm not mistaken, the only reliable way to test the PSU output is with a voltage meter or a dedicated PSU tester (Example)
. As far as checking the capacitors, you may need to open the case. Of course this will void any warranty you have and there could be residual energy inside, enough to hurt you, so beware.

 

If you can, swap out the power supply with another computer and see if the problem moves.