Hello, I'am microsoft member like you, so can you access to the windows? If yes, then try running a SFC and DISM scan to check for corrupted/missing system files, because it may be the cause, and then run a virus scan, most of the time, the malwares are
the problem, I recommend you to run thos two on Safe Mode, If you can't access to windows and safe mode, then pick your windows installation, put it in your PC, boot on it, After that, click on repair my PC, then Do the starup repair, If he did find nothing,
then run a command prompt and type: sfc /scannow, after finishing run: DISM /Online /Cleanup-Image /ScanHealth.
Im not sure about this, Im just trying to help, hope i helped you!