PC stuck cycling on/off on power up.

My pc has been working fine for ages. I’ve been playing MSFS2020 which occasionally would freeze the pc. It did this again a few times today. However on the last time. The PC is stuck in a cycle where it powers up for maybe ten seconds then goes off and repeats.
Spec:
PSU Corsair CS650M
gigabyte Z170 Gaming K3
DDR4 Ram. Corsair 2x8GB and 1x 16GB
NVIDIA 1070 graphics

I’ve tried removing each Ram stick at a time. Powered off and left for a while. Unplugged and refit the graphics card. Completely stuck for what else to try. Any suggestions?

thanks.

I’ve managed to get it working. I removed the GTX again, gave it a good blow of any dust (there wasn’t much) and replaced. Did the same again with the ram. And tried initially hdmi from the motherboard without the gtx in. That worked. Replaced the gtx and it worked fully again. Left it running now for a bit see what happens. Machine is 3 years old.

Spoke too soon. Left it switched on for a couple of hours. Came back to find it first hung on the bios load screen. Turned it off and on and now it’s cycling on/off with power every 2 seconds.
I removed the NVIDEA, but still cycling power.
removed one 16GB Ram. This time power stayed on a little longer then restarted. Didn’t get far enough to load bios. removed second ram. Booted up ok. So, perhaps it’s a faulty Ram? I placed the first RAM back into the slot the 2nd one was taken from. Left switched on again for a short while to see what happens.