1999 Ford Taurus Question: Car stalls in park & driving sometimes. Starts up again after it sits for a bit

This has happened 3 times in the past few months. The first time - it stalled when I put it in park in the driveway after driving it to and from and appt.
The second time - it stalled while I was driving it slowly in a parking lot.
The third time - it wouldn't start again right away shortly after I parked the car.
Each time - I let the car sit for around 30 minutes and it started right up again.
Mechanics ran diagnostic on it, and tested fuel pressure, and both came out fine.