Random power surge warnings

[Syri]

Recently, my PC has started randomly restarting and issuing a warning that a power surge was detected. Nothing has changed hardware wise, and it has ran for over a year before this problem started. It first happened a couple of weeks ago, and has been going on and off since then, sometimes several times a day, sometimes a week or so without any trouble. There's nothing I can do that will guarantee it will happen, so far, it just goes at random.
I've had it occur only when playing games so far, either with the game in foreground or background. It's happened while playing WoW and Guild Wars 2, but not every time I play those. I've played more intensive games, such as GTA 5, without any problems, and also done CPU/RAM/GPU stress testing without problems, using 3D mark and Prime95.
I've seen some posts while searching, but most seem to be down to cheap PSUs (which mine isn't) or glitches in the monitoring system, which I'd expect to have shown before now, and not only when playing games.
System spec is as follows:
CPU: Core i5 3570 @ 3.4ghz
RAM: 16gb ddr3
MB: asus p8z77-v lx
Storage: 2x samsung evo SSD
GPU: zotac geforce gtx970
PSU: corsair CS650M

If anyone can suggest anything that might either narrow down the cause, or possibly help to reproduce it more reliably so that I can narrow it down, I'd welcome any ideas. So far I'm wondering if the PSU could be overheating, and if that could cause voltage spikes if it were, as when the problem does occur, it seems to then be more likely to happen after restarting. The CPU and MB temps are well within safe levels, so I don't think either of those is overheating, nor would I expect either to cause these symptoms.

 

[caLLous]

Try running the computer with the PSU outside the case and see if it happens (although if you're internal temps are good then overheating won't be the issue unless something has gone wrong inside the PSU itself). Try reseating all power cables (especially to the motherboard).

Got a spare PSU you can swap in for testing? Components fail, Corsair are one of the better brands (even though they don't actually make any of the PSUs that they sell I believe) and the CS line are fairly decent re: build and component quality but if something has gone inside it then it could lead to it being temperamental. I think you have a 3 year warranty on it so it might be worth pursuing that or just buying another (this one could be relegated to a spare, it's always good to have a spare).

 

[Syri]

Well, after trying as much as I can without swapping components, as I don't have any spares to try, the graphics suddenly started showing distortions in games. After some attempts to fix it, with things like driver updates and such, it got worse and worse, until windows stopped booting with the drivers installed. Going to try the card in another PC if I can, to be sure, but looks like the graphics card has died, though whether it was the cause of the problem, or killed by it, remains to be seen...