After effect preflighting
I assume that after effects is creating its cache-files on the c-drive (which is the standard location if I recall correctly) and because there is near to no space left, it struggles to cache frames. The first thing you can do is go to edit -> purge everything and see if that helps. In any case, I highly advise you free up your c-drive - I'd feel comfortable with about 100-200gb of free space (at least)