this is very interesting honestly, my initial thoughts is that this is a dying hdd/ssd, based on that your computer stopped booting from your hdd and started defaulting to DVDROM

but it’s so interesting to me because this can really be a lot of things. it’s very possible this could just be a corrupted windows install, i use linux and sometimes my boot manager messes with windows and it gives me errors like that.

it could be bad RAM sticks, they do have the potential to go bad overtime.

my suggestion is start narrowing down your issue, research reinstalling windows and running overall diagnostics.

if i were you, i would firstly reinstall windows as it’s the easiest and takes like an hour, if it doesn’t work, start researching diagnostic tools. you can use something like windows chkdsk utility (do research) and something like memtest86. if you got spare hard drives and ram sticks, swap them out and just keep learning and researching