[HELP]Computer's on then goes off

[marklabuga_]

I bought this pc last december.
It was great and runs fine until awhile ago.

My cousin's friend stop using this pc and so its my turn. But then the screen is hang so I restarted. And then this problem exist. Power goes on, fans were running, then 2 seconds, it stops. Then repeat and repeat and repeat.

Please help.

Here are my specs.

i5-4460
H81m-DGS R2.0 ASROCK
AcBel R8 Power II 550w 80+ Bronze
Kingston 1600Mhz 8GB DDR3
EVGA GTX 750 Ti 2GB FTW
500GB Western Digital HDD

 

[JQB45]

Replace the power supply. I had the same problem, a new quality power supply resolved the problem
Choose a Tier-1 or Tier-2 Power Supply from this list: http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

If you can only afford a Tier-3 unit those are Ok. Tier-4 and Tier-5 should be avoided.