Major problem that I can't seem to solve

I recently built a pc and intitially in first boot the monitor wouldn't recieve signal from the GPU so I assumed the GPU was the problem. But eventually i got it to work. However, when i first tried to play a game the monitor lost signal. Again i thought it was the GPU. I tried switching PCI sockets and thrn the PC became stuck in a loop (boot for 2 seconds, dies, boots for 2 seconds, etc). I took out the gpu and this continued. I reduced it to just a stick of ram thr mother board, the cpu and the PSU. And thr PSU didn't start at all and only made a buzzing noise. This morning however it seems to be back to its constant loop. I think it's the PSU but I don't know if that would cause the problems stated earlier.

System: Gigabyte H97m Mobo MSI GTX 970 GPU I5-4590 CPU Seasonic G 650W PSU Kingston hyperX 2x4gb Ram Cooler Master Hyper 212x CPU cooler