<<<<...you should check all the ground wires and
make sure they are not corroded. There was also a recall from Volkswagen to
add a ground wire (for what years??).>>>

I had this same problem.  Crappy ground strap on the driver side of the
engine, corroded connections at the front of the tranny.  My starter was
trying to pull the ground through my exhaust, where it was wired to the frame
with a coathanger.  (note: a coathanger is a tool of last resort, only used
for emergencies)  Coathanger got hot and burned me, that's how I figured it
out.

I cleaned all the contacts, then decided the ground straps were really crappy
looking, so I added a big fat wire straight from the battery to the front of
the tranny.  It was big, like 4 gauge, the same as you use for the battery
terminals.  I coated everything with dielectric grease, and cranked that
puppy down.  The wire was just snaked through the hole in the bottom of the
battery tray, over the gas tank, along the frame, beside the coolant hoses.
Held up with zip ties. Attached to the battery using the screw for the
terminal.

Bill Marshall
85 GL Tiico with no more coathanger