I have had several of these cars, and it sounds like it is either the ignition module or the crank sensor gone bad. When the engine warms up, broken contacts in the components expand and break the circuit. When it dies, does it turn off just like a switch, or does it stumble like it is starving for fuel?
Of course first you should see if it is a fuel or spark problem. When the car dies and wont restart, pull a spark plug wire and check for spark.
Ive had to replace several ignition modules on these cars, but never had to replace a crank sensor (though I know a few who have had to). The ignition module is more costly, but easier to replace.