Is there a common problem with this car that causes the engine to not restart about 15 minutes after the car has reached operating temperature?
Won't Restart on 1995 BMW 540i
it is usually one of the engine sensors either camshaft or crankshaft sensor. more often camshaft. once engine cools it reads again fine and statrs car ok. when car is running again the ecu will only require one or other of the sensors. my guess is you also have a roughish idle. get the car plugged in at an indy and see which sensor you need!