Hello everyone, i'm new to this so i might do some mistakes.
Here is my problem: My pc doesn't start when i put my gpu in the motherboard and plug in my psu cables into it. But when i unplug the psu cables from the gpu and just leave the gpu in the motherboard and start the pc, everything starts for a second and shuts down, but the gpu fans try to spin, stop, try again, and its like they have no power to do so, and i'm very confused is there more likely to be a problem with the psu or gpu? I don't have another psu, so that means i can't test my gpu, i will get it tested tommorow, but i really want to figure out whats going on. Other parts of the pc seem to work fine. And my pc starts without the gpu.
GPU: EVGA GTX 970
CPU: I5-8600K (just upgraded)
Motherboard: MSI Z370-A-PRO (Just upgraded)
RAM: HyperX Fury 16Gb 2133Mhz(New, but i overclocked them a bit (2433 i think))
PSU: Cooler Master ThunderM 620W
I have a cpu cooler 3 case fans an ssd and hdd, but i don't think those matter.
I will be really thankful if someone has any idea what could be wrong.
P.S No major overclocking was done on the gpu, no voltage was changed ever. And i kept my gpu fairly cool. I have my gpu for 3 years now.