[SOLVED] System switches on, then off, then boots (power issue??)

[psy1]

OK basically here's the best description of the problem I can give:

I recently installed a PCIe wi-fi adapter; the Asus pce-ac88
After I installed this I noticed once I hit the power button, my PC would start up, then switch off, and then after a few seconds boot up again and then successfully boot up into Win10.

I've reinstalled Win10 and reinstalled all fresh drivers and stuff. I've also done quite a lot of hardware troubleshooting. I haven't found a solution to the problem yet.
I'm very confident that the problem is not driver/software related.

Could be a power supply problem? My power supply is a 600w Silverstone Strider Titanium ST60F-TI reviewed right here on Tom's Hardware: https://www.tomshardware.com/reviews/silverstone-strider-titanium-st60f-ti-psu,4556.html
600w should be more than enough wattage. So, I'm not sure even if the problem is the PSU.

Here's a vid I uploaded to Streamable showing what's happening: https://streamable.com/aikvik

Any clues to help me diagnose what's going on?

 

[Lutfij]

We're going to need more information. Please include/list your specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU: age
OS: version for the OS.

By installing the drivers, do you mean installing them manually after sourcing them from manufacturer's support site? You might want to see if your motherboard has any BIOS updates pending. Dark video looks like you own an NZXT S340 Elite.

 

[psy1]

Hello and thanks for helping Lutfij,

CPU: Ryzen 1700
Motherboard: Asus Prime B350 Plus
Ram: G.Skill Flare X 16GB (2x8GB) 3200MHz
SSD/HDD: Samsung 960 Pro 512GB, 8TB Seagate Barracuda HDD
GPU: Sapphire RX 480 (4GB RAM)
PSU: age, about 2 and a half years (varies depending upon part, wifi adatper and RAM are brand new.)
OS: version for the OS.: Win 10 Pro, version 10.0.19041 Build 19041

System was a 'slow build' most parts are only about 2 years old, some are brand new like the RAM.

I'm a "semi-expert" builder/troubleshooter, so I can answer all your questions and follow all your instructions.

"By installing the drivers, do you mean installing them manually after sourcing them from manufacturer's support site?"
Yes

"You might want to see if your motherboard has any BIOS updates pending."
Done that.

"Dark video looks like you own an NZXT S340 Elite."
Correct

I'm really hoping to get this problem solved.

 

[psy1]

PROBLEM SOLVED: turned out I didn't fully test the PCIe slot and that was the problem. I just transplanted the wireless adapter into another slot and the PC boots fine now.