Question New build shuts off after a few minutes

[LafferCurve]

New to the forum but hoping someone can assist.

I recently built my first PC and powered it up straight away, no issues. I used it for a few hours the first evening again, with no issues. The next day (before powering back on), I installed a wifi adapter and attempted to power back up. It worked fine for about five minutes, and then shut off. The power button light stayed on, but everything inside the case seemed to die. No fans, lights, etc., and the power button wouldn't turn the computer back on. After unplugging from the wall and re-plugging in, it powered back up, but only for about 10 seconds before experiencing the same issues. After that, only the occasional fan twitch with a flash of lights and eventually no activity whatsoever.

I took the PC into a repair shop and after a couple of days they said they re-seated the GPU and RAM and it 'consistently powered up.' I powered the computer back up at home and after five minutes, I ran into the exact same set of issues.

I'm currently working through the common 'not booting' checklist but as I've successfully used the computer for several hours, can anyone point me in a specific direction? I don't have a spare PSU or any other parts to swap out as this is my first build.

My specs:

• AMD Ryzen 3700x
• EVGA Geforce RTX 2060
• Gigabyte B450M DS3H
• Team Group TLZRD416G 3200H
• Corsair CX550M
• Western Digital WDS500G2B0B 3D NAND Internal SSD M.2 SATA
• ASUS PCE-AC58BT (no issues until this was installed)

Thanks, hoping someone can point me in the right direction!

 

[LafferCurve]

Update - I have taken motherboard out of case and breadboarded. As I was unscrewing the motherboard I noticed one of my screws was going directly into the case, not into a standoff. Did I get lucky the first time I powered up only to eventually short the motherboard?

I currently only have the CPU and PSU plugged into the motherboard. The screwdriver short trick powers on the CPU light and fan for just a second, and then nothing. Does this mean my motherboard is dead? Or must it be something else if it's powering on at all?