PC freezing randomly while playing games

[macman241]

Ever since a few months my PC randomly freezes after a random time of gameplay on most games - this time period could be 15 minutes, or it could be 2-3 hours or it could not freeze at all. However, I feel like recently this has been happening more frequently. The PC will freeze without any warning whatsoever, and I will need to hold down the power button in order to restart the PC. I am not overclocking. My temps do not reach high values in most of the games where it freezes. I am using an i7-6700k, a gtx 970 and a gigabyte motherboard. My OS is Windows 10.

Things I have tried:
-updating drivers
-changing power settings
-scanning drives for errors
-memory test

I also tried updating my BIOS, but the BIOS does not see the update file from my usb. I have got no idea how to diagnose the problem. Any help would be much appreciated.

Also: If it is deemed to be relevant, when I first built the PC (4 years ago) I had RAM issues where the RAM would get underclocked when the PC is idle and the same type of freezing would occur (except not in games - this was fixed by updating the BIOS).

 

[Ramlethal]

What PSU do you have exactly?
How many Ram slows are you using and what frequency, brand and capacity are them ?

 

[macman241]

What PSU do you have exactly?
How many Ram slows are you using and what frequency, brand and capacity are them ?

PSU is evga supernova 550w
2 ram slots, 2133MHz, corsair vengeance 2x8GB

 

[Ramlethal]

everything seems quite fine, Could be a windows 10 issue? Did you by any chance recive any BSOD message in any of those freezes or it just freezes and goes dead until you restart it ?
Also, you can try removing 1 of the Rams and playing with only 1 slot of 8gb and check if it keeps going the same. If it does, remove the other one and try the one you removed before and if it keeps doing it. Then, well see later what else could be...