my computer shutsdown randomly

[veny]

my newly built computer shutdowns randomly and it cant be turned on until I unplug it for a while, no matter if it's under load or not. it's usually happening once a week or two but some days it happens multiple times and after that, it's ok again for a week. I have already posted a topic about this.

 

I am asking here because its probably faulty power supply but it doesn't make sense to me I have evga 750 g3 which is not the best choice I could made as I learned here 

but the problem with evga g3 is exactly opposite to mine the protections trigger to late.

Can it be bad motherboard? I dont want to buy power supply and realize its faulty motherboard and return it.

 

[veny]

according to https://outervision.com/power-supply-calculator 750w should be egnought  

[SupaKomputa]

550watt should be enough for any PC.

THe problem may not be your PSU, it can be anything else.

[veny]

and one more thing after it shuts down and can't be turned on by the buttons on the case I can still turn on the psu by shorting pins 14 and 15 on  the 20 pin conector