May be an ignition modual problem. The ignition modual is under the distributor cap. Get an AC Delco replacement one as others seem to be crap. If you replace it make sure you smear on heat sink grease on the bottom of the modual (available at Radio Shack).
The modual overheats, killing the engine. The car cools down and it works for a while.
Also there may be an ignition coil issue, but I'd do the modual first.