Help. Computer randomly freezing and crashing.

[Piggyyy]

I just came back after being away for a month and so far my computer has crashed 4 times. The first time was while I was watching a video and the computer started hanging and I had to do a hard reset. The other three times were while I was gaming, two of the times the computer just started hanging again and the other time the computer just turned off by itself. Does anyone have any advice on how to troubleshoot or what the problem is? Thanks.

My specs are:
i5-3570k
gtx 970
16GB ram

Update:
It just crashed again while I was posting this and I tried moving my RAM around. Then when I turned the computer on it said overclock failed while booting so I tried setting my BIOS settings to default.

Update 2:
It's crashing even more now and it's starting to take multiple attempts to restart the computer, could my power supply be dying?

 

[Diddly]

make sure all the fans are still turning properly after being left switched off for so long. check all power leads are still connected properly on the mobo. remove as much dust as you can too.

 

[Piggyyy]

make sure all the fans are still turning properly after being left switched off for so long. check all power leads are still connected properly on the mobo. remove as much dust as you can too.

I checked all the cables and nothing was loose and all the fans are working properly. My computer started hanging again while I was trying to type this response and it took two tries to turn it back on, the first time it just turned off right after pressing the power button.

 

[Diddly]

Maybe the PSU is knackered then. do you happen to have a spare?

 

[Piggyyy]

Maybe the PSU is knackered then. do you happen to have a spare?

Yeah I was thinking it might be the PSU dying too, but I don't have a spare to test out.