The disk itself is only a few months old, it didn't got hit or anything so i hope there's no HW failure incoming.
If i lose those 3tb of data i'm going to be very, very sad, lol.
If it was me and the PC booted and I got into Windows I'd hook a USB HDD up to it and pull/copy all my important data off.
I would do this prior to any other efforts......
HDDs drives are known to crash in my experience in four main scenarios.....
1) Old and just too much wear over time......this can be many years though.
2) A hard drop....usually from dropping PC.
3) Heat.....HDD running at 55C+ will die fairly quickly.
4) Infant Mortality....which is what I think you have....basically a bad HDD that exhibits early in life cycle.