I had the same problem too with 94 regal 3.8. Mine started off stalling once in while and over a couple of years it would stall or not restart after driving it and parking it. After replacing crankshaft sensor, I've been good since November. It fires right up all the time.
I've learned that if the sensor intermittently fails, the ecm doesn't get the signal to give spark.Good luck and post your results.