Maybe I didn't read carefully but:

Can this also be spark related? Would there be a code that can be read that might help? Could there be some kind of electrical connection that goes faulty when the car hits a bump? TO me the puzzle is how it can it restart right away.On my old 940 the impulse sender would quit but I could re-start after an imagined 'cool down' - maybe the contracting contact worked when it got cool. Dunno. Is there something that controls fuel pressure so that when the car is off the pressure lessens to the point that the pump can again start to work? But what force is occasionally hi or lo and then after some time returns to normal? Pressure, heat, electrical charge (capacitor somewhere). If you do seem to locate the faulty part it would be interesting to keep testing to see what the problem actually is with the part and also to prove that it is definitely the cause.