I had the same problem with my '90 Crewcab.  After some time and effort
the fault was traced to a temperature sensitive piece of electronic
stuff in the distributor.  I had to put a new dizzie in ($$$$$$$$) and
that solved the problem!

Joseph Roy, Ph.D. wrote:
>
> "84 Westfalia water-cooled has "intermittent" starting problem after
> driving
> in town or on highway. When attempting to start after driving, there will
> be a momentary engine firing and then no ignition. The motor will turn over
> without starting. Additional attempts to start only flood the motor. Let
> the van sit for 30 min. to 2 hours and it starts slowly. Cold starts are
> always instantly successful. Two local VW mechanics have given it there
> best efforts with no success. At this point, I don't find a pattern in this
> intermittent problem. It's is very frustrating because I never know if the
> van will start. For example, if I kill it at a stop sign... Thanks for your
> suggestions.