Build turns on then shuts off after a split second?

[Agronack]

Hello everyone, I've Googled, as well as read up on these forums problems similar to mine but I still can't come to the conclusion of what's causing the problem.

I built my computer around 3-4 years ago, then upgraded some parts a few months ago. I haven't brought it up to college yet and therefore haven't used it often over those months, and am down for Spring break. I used it the first few days completely fine. I woke up this morning to turn it on, pressed the power button, the LED's, fans, and everything come on and a split second after everything completely shuts off. Upon pressing the power button again nothing happens (I have to unplug or reset the power supply in order for it to turn on for the split second).

Does it seem as though it's the power supply and where should I start to trouble shoot?

Thank you

 

[plankingdom]

The power supply can be on its last legs, and still be capable of power, but at a severely diminished return.

Power supply should be your full check. Swap it out for another, you can buy one from a local computer parts store then return it if needed. One I used to live by never had an issue with it as long as you returned it undamaged, and were forthcoming on your intent at the time of purchase.

If nothing comes of that, try the same thing with your ram. If you have 2+ sticks, try them each one at a time in different slots.
Do that with each of the 5 major parts. (PSU, RAM, CPU, GPU, and Mobo)