If this is a manual transmission then the starter bushing could have
completely failed and worn through.  The starter would have to be removed
to check.

Recently I was having starter problems and the bushing was worn.  I found
that even a new bushing would not help because the hole in the
transmission bell housing was so worn that a new bushing was not a snug
press fit.  I think the usual temporary fix for this would be to epoxy
glue in a new bushing.  As this was on a Kennedy adapter plate Subaru
conversion with a VW starter I used the High Torque adapter from RMW and
installed a TDI starter which is self supporting like automatic
transmission starters and doesn't require an end bushing.