Desktop turn on problem. Help Please!

[Cisco001]

I installed my set of used motherboard, cpu, ram and ssd with my brother old case and psu.
I need to hit the power button a few time to turn it on.
The set of hardware don't have such problem in mine.

Do you think this is the connection problem of the PC case, or the problem of PSU?

 

[johnb35]

Build it outside of the case to verify its not shorting out against the case first and then go from there.