1999 Ford Taurus Engine dies after warm-up

Occasionally (once a month or so), my 1999 Ford Taurus engine dies and the service engine soon light comes on - - this only happens after the car has been driven an hour or two. After about a 15 minute "rest" it starts right back up again, the service engine soon light goes out and the car runs perfectly for another month or so. This car has been babied and kept stored in my garage since new. The only thing I have not done is flush the radiator and put in new coolant - - I will get that done soon. It seems that this only happens on warm days when my wife is driving the car to local stores. She always has the A/C on max and starts the engine repeatedly after each store stop. She gets very upset when the car leaves her stranded - - even though it starts up again after a 15 minute "rest" period. I am reluctant to take it to a mechanic because I can't show him how the engine dies for no apparent reason. I think it is a PCM problem but how does one know for sure? Does it store a malfunction code each time the engine stops running? Or does it reset itself and leave me without a clue why it stopped running? I have to get this fixed - - my wife is afraid to drive the car now beacause she doesn't want to get stranded somewhere - - especially at a traffic signal - - she can't push the car over to the shoulder by herself.