Windows 10 Desktop PC spontaneously became unable to boot (goes to blue screen). I'm unable to boot from USB either

TL;DR -- PC boots to BSOD. Cause is unknown. bootrec fixes didn't work. Booting from USB also goes to BSOD and can't access troubleshooting mode anymore.

My Windows 10 Desktop PC seems to have spontaneously stopped working yesterday and I'm at a loss for how to fix it.

For some context on why it was spontaneous: it was working fine in the morning but when I came back in the evening I was greeted by a Blue Screen saying "Startup Repair couldn't repair your PC" and then giving me the options to "Shut down" or enter "Advanced options".

Not wanting to reset my PC without first trying some fixes, I did some googling and found some answers that suggested running the commands BOOTREC /FIXMBR, BOOTREC /FIXBOOT and BOOTREC /REBUILDBCD from the Advanced options Command Line Interface.

I tried running those and they all worked fine other than /fixboot, which gave me an 'Access Denied' error. Some more googling on that error offered me some more solutions, which I tried but they didn't work. I then left my PC for the night.

When I came back to my PC today I decided I would just try and reset it so I made a win10 iso on a USB, booted up my PC, entered the BIOS and set the USB to be the boot device. But even trying to boot from the USB gives me a blue screen error saying "Recovery. Your PC couldn't start properly. After multiple tries, the operating system on your PC failed to start, so it needs to be repaired. Error code: 0xc0000001". I am then presented with "Press Enter to try again" and "Press F8 for Startup Settings". I have tried all options presented multiple times but none have worked.

On top of that, I no longer seem to be able to access the Startup Repair Troubleshooting screen no matter what I do.

Any help or advice would be hugely appreciated as I'm not sure what I should do if I can't even boot from a USB or access the troubleshooting page.

Thanks!