BIOS start up

So long-ish story but looking for help. I bought a pre-built in 2016-ish in 2021 I essentially built a new computer but kept the hard drive and case from the prebuilt. In 2023 my wife found two computers that someone was throwing away due to what appeared to be broken cases. Well the end of 2023/beginning of 2024 my pre-built hard drive was full and would no longer start up due to insufficient storage (only 128gb ssd) I took an m.2 from the better looking pc’s my wife found wiped it clean reformatted it etc. and installed windows on it (sketchy I know) but it worked for a over a year. Then about 3 months ago my computer would throw random error codes and random start shutting off or restart and going into the BIOS menu. I assumed it was the hard drive going bad. Today I went and bought a new M.2 and tried installing windows from a thumb drive but it still keeps going straight to the bios. The boot sequence shows the thumb drive (an actual windows thumb drive purchased from micro center) but won’t boot from the thumb drive even though it has in the past. Any help or suggestions would be greatly appreciated.

TLDR: Computer randomly restarts into bios/ trying to install fresh windows on new hard drive keeps booting into bios.