Question PC keeps cycling on and off. I've run out of ideas. Do you have any?

[Rodenberg]

Hi fellas.

So I've got this PC that keeps cycling on and off, every time I turn it on. I've tried reseating the RAM in all possible combinations (and tried just one at a time), cleared CMOS and now after buying a new PSU, tried that one on for size.

It's still cycling.

Do you have any ideas on what to try next?

Thanks a bunch.

EDIT
This is an older PC - first one I ever built.
G3258 Anniversary Edition
Gigabyte GA-H97M-D3H
2x2GB DDR3 + 2x4GB DDR3
No GPU
Corsair VS350 (and Kolink Core 300W)

 

[TouchPlayTV]

Give me your PC specs include the RAM speed

 

[Dark Lord of Tech]

Corsair VS350 (and Kolink Core 300W) ...You tried 2?

 

[Rodenberg]

Corsair VS350 (and Kolink Core 300W) ...You tried 2?

I did try two, yes. So I'm very much assuming that it's got nothing to do with the PSU. Now I'm looking for some way(s) to locate the problem.

 

[Rodenberg]

Give me your PC specs include the RAM speed

I'll get right on that as soon as I am able to look at them. I should note that they have been running together, all four slots, for more than a year with no problems, so it's not because I recently changed anything.