Computer Randomly shuts off

[MaxMalvin]

Hello, so today i launched up GTA V.  Played for 40 minutes. And the computer restarted for no reason. This has happened before.  For example in Star Wars Battlefront 3. Although it only restarts if i start up my computer and jump into the game directly.

System specs:

CPU: FX 8350 ( Black edition, Cooler: CM Hyper evo 212 )
GPU: R9 290 ( Reference model )
MB: Sabertooth 990FX
PSU: Corsair 750W ( The PSU is pretty old )
RAM: 4x4GB Corsair Vengance 1600 MHz ( 2 of the ram sticks are low profile )
Chassi: NZXT H440W Silent Ultra

FANS: 

Front: 3 120mm
Back: 1 140mm
CPU fan: Hyper 212 EVO

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There are two things i think are the cause of this.
The first is that someone suggested that the ram may overheat since GTA V does have known bugs for Memory leakage ( Dont know if its true or not ) 
The second is that the PSU may be getting old, and that it does not commit as much watt as it is supposed to do.

I've checked the temps via HW Monitor. The CPU temps seem to be around 50c.
I've gone into the AMD's Overdrive, increased the fan speed to 49 maximum and set the target temp for 88C

Screenshots of event viewer:

http://imgur.com/W40sYuY



 

[LiamApex]

could be the psu

[Tedster]

could be the psu

This, I'd blame the PSU.

[MaxMalvin]

Do you think the PSU is overheating by any chance?
Is there anyway to check if it's overheating?