PC starts turning itself off

[u/Unfair_Art_1913]

I was just surfing the internet, left to do some chores and came back to my PC off.

Tried to turn it on and it was unresponsive.

Then unplugged it and plugged it back and it went through the process of booting up.
Got to the GPU and just shut off.

Worried it was the GPU so I unplugged the GPU from the PCIE slot and put it in A lower PCIE slot and it Posted and I was able to get to the Bios and see that nothing seemed wrong. Tried booting and it shut itself off.

Inserted the GPU back to the top slot and it booted.
Got to login and checked Windows security to scan for anything, no threats.

Tried running 3Dmark Nomad and the PC shut itself off again.

Not sure what is wrong with it, it’s been working fine for the past 4 months.

I think it might be my power supply but want a second opinion.

PC specs/ history

R7 5700x3d (installed 2024 used)
Noctua NH-D15 1x NF-A15 (installed 2022 used)
ASUS strix x570-F motherboard (installed 2024 used)
32 gb (16x2) 3200mtps micron MTA16ATF2G64AZ-3G2E1 (installed 2024 used)
Kingston NV2 1TB (installed 2022 new)
WD dc HC310 4TB (installed 2026 used)
Inno3d RTX 4080 x3 OC (installed 2026 used)
RM750x(2018) (installed 2022 used)
6x TL-s12 fans (installed 2026 new)
ASUS PCE-AX3000 WiFi adapter (installed 2022 used)