03 expl stopped running while driving. I restarted it,what would make it quit?

If you lost all power to the vehicle, radio, and gauges you may possibly have a bad battery or a bad connection at the battery. A bad connection at the battery would cause the vehicle to die and since it's just a bad connection it may have made a good connection again allowing the vehicle to start.

Crankshaft position sensors can cause that and most of the time it does not throw a check engine light. Hard to diagnose if it is intermittent.

I would check the power wire that comes off the positive cable. Wiggle that wire while the car is running and if it shuts down you have found your proble. If it does not shut down you probably have a crankshaft sensor problem. Intermittent problems are very difficult to diagnose.