When I press the power button, my computer turns off almost immediately.

[Ricewick]

I just built my PC, and everytime I press the power button, the cpu cooler rotates, the graphics card lights up, and the fans on my GTX 950 rotate but after a second or so, it will just stop.

 

[Someone Somewhere]

http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

 

[PokerTroller]

Maybe your PSU wattage isn't enough. What PSU do you have?

 

[Ricewick]

Maybe your PSU wattage isn't enough. What PSU do you have?

I have a Corsair CX 500