Booting computer it shuts down after few seconds and then starts automatically normally

[bigcat1]

I just buildet new computer and when i try to start it it shuts down after few seconds booting (shutting down like your computer cant get power) then it reboots automatically and starts normally. i have no idea whats wrong after running normally and doing restarts/shutting down/starting it proceed normally its just the first boot. any ideas?

Specs.
Asus GTX 760OC
lntel Core i7 4790k 4.8GHz
Asus Extreme Ranger
Samsung Pro series 840 240gb
A-Data 2x4GB
china power 500W
Windows 8.1 Pro

 

[royalcrown]

I am going to GUESS here that your power supply is unstable junk.

 

[bigcat1]

thanks, gonna buy tomorrow new power, will see mb it helps

 

[bigcat1]

Resolved!

New power didnt help.

Installed newest bios, works now perfectly!