PC with GTX 970 shuts down when playing game

Hello! I'm having a problem with my new budget build. Actually several problems. First, it shuts down, when I'm a few minutes in game. My GPU is Palit geforce gtx 970 jetstream, This is actually the 2nd GPU I try, the first was Gigabyte radeon r9 290, but it made my pc to restart constantly. I was thinking that it might be PSU (I have 600W Corsair CX600), but gtx 970 requires only 500W. Could the PSU be faulty? Another symptom I experience is that the monitor receives signal only every other time I tur the pc on. The rest of the 50 % it just shows "no signal". In those "no signal" situations motherboard does not make the normal single beep, but several beeps, maybe this info is of some use?



Pc also gets a bit too loud when working for a longer time. I measured GPU temperatures, it starts off with 39 degrees Celsium, when I started the game (Far Cry 4) it was 72, then it dropped to 64. After that it shuts down. Fans are running fine when it goes above 60.



Another weird thing is that my 24 pin cable does not sit very well in the motherboard, I pushed it really hard (there is almost no gap now), but I did not hear any click or something. Maybe there are some power exchange problems?

Thanks in advance! And sorry for silly questions, I'm new to all of this. :)



Rest of my specs:

ASRock 980DE3/U3S3

AMD FX-6300

8 GB RAM

PC with GTX 970 shuts down when playing game