Why Does My PC Shut Off Within a Minute of Booting?

I recently completed building my PC after a lot of effort with parts fitting and everything. However, when I tried to boot it up for the first time, it shuts off after about 40 to 60 seconds. During the boot, everything seems fine at first—fans are running, and I have video output. But then, the PSU fan stops, the other fans slow down, and finally, it powers off completely.

I've tried a couple of power supply units (one at 750W and another at 500W), and they both had the same issue. I've checked the thermal paste and looked for any damages on the CPU and socket, but everything seems fine. The GPU is functioning since it provides a display output, and I've reseated it. I also reseated the RAM with no issues detected.

At this point, I'm starting to wonder if there's something wrong with the motherboard or if I might have overlooked something, even though I've inspected everything thoroughly. If I don't find a solution soon, I'm considering returning the motherboard to see if that's the culprit.

Here are my specs:
- CPU: Ryzen 5 7600X
- Motherboard: Asus TUF Gaming B650 WiFi Plus
- GPU: RTX 4060 Zotac
- PSU: Asus TUF Gaming 850W Gold 80
- Cooler: Thermalright Peerless Assassin 120
- RAM: Kingston Fury Beast 8x2 DDR5 5600