The computer boots to the blue screen of death with the message 'Inaccessible boot device'
Windows 10 uses multiple partitions and the C: drive you see is not really the boot partition. For some reason it's not loading the operating system.
It is a scary message. A reboot may just take you to the same thing. Do not follow the advice that you get from the internet and start reinstalling Windows. It's a poor solution.
Don't forget that if you reinstall then you will lose everything.
Reboot again and try hitting F8. See if you can get into a Command Prompt screen. If you can you may find you end up at an X: prompt with a few directories in it. You will find there is a C: drive but it's not your normal C: drive. If you look at D: then you may find all your files and folders here.
Run sfc /scannow on any drives that you find. It may say that it has found nothing.
Reboot again. Does the computer now magically reboot?
Worth a try.
This may be connected with pressing reset when the computer hangs for a very long time on startup when it's actually doing an update.
Norman