Question PC Problems: BSOD, random Reboots and No Video Signal

[john-9023]

Build:
i7-4790
MSI z97m
2x 8GB ddr3 1600MHz Corsair Vengeance
Nvidia gtx970
Corsair cs650m

For some time the PC had freezes with buzzing sound ending in BSOD. It was necessary to reboot (via the button on the case), in some cases even twice because after the first one there was no video signal.
Then one day after turning on the PC, it restarts two or three times by itself and when it manages to "stabilize" and turn on there is no video signal.
I tried to restart both with the button on the case and directly with the button on the motherboard but it does not restart and on the debug display of the motherboard the series of codes always ended with b2 which, for the little I could understand by looking at the manual, corresponds to "late south bridge initialization".
Then I tried to do Clear CMOS via the button on the back of the motherboard and connected the cable to another display port of the GPU.
After that, I tried to turn on the PC and after a message on the screen that said to press F2 to continue it started normally.

What could be the problem?

Thanks

 

[Paperdoc]

My speculation only - NOT a "for sure"! I suspect the PSU is weak or failing. I note that your PSU's power rating should be enough for that system.