[Troubleshooting] PC turns on for 15 seconds then shuts off and turns back on again.

So my PC will turn on for 15 seconds the instantly turn off and then rinse and repeat, no picture on the monitor, was using the integrated grahphics of the CPU.

If I take out the RAM the PC will be on indefinitely and will not turn itself off, however if I put the RAM back in, it will return back to the same cycle again. I already bought some new RAM because that is what I thought the issue was but the same thing is happening.

The reason I thought it was the RAM is because I unplugged literally every last thing except for the PSU MOBO and CPU and it seemed to power up, however since I don't seem to be getting a display is it possible that it is my motherboard or CPU instead?

Any ideas?