my 92 jetta gl had a similar problem, used to not start after driving for awhile and shutting it off (no stalling though). Then it would randomly start an hour or so after that. I thought that it had to do with the heat because eventually it would start again. But the solenoid in the starter would go out periodically and not start at all. Alternator always tested fine. Battery fine, cables fine, etc. Eventually i was on the 3rd new starter and about to ditch the car. it ended up just needing a 12v booster relay to the solenoid, and voila no more burning up starters. (thank you usenet) then I gave that pile to my sister anyway and got my EK
anyway sounds electrical to me.. have you searched for recalls? try a google newsgroups search as well.. good luck..