Best to get someone to check the system for any faults recorded by the engine management system. The fact that it cuts the engine but once you cycle the ignition it starts again would indicate a fault with the electrical side of things, perhaps a crank sensor failing. The next time it does it, while you are still on the move switch the ignition off and then on again (don't take the key out!!) if it's a sporadic electrical fault it'll probably fire up again and run so you won't have to pull over.
One things for sure, get it checked out because somethings about to go and when it does you won't be able to start it again!
Might be worth sticking the fault in google, it may be a known problem and you could pick up some info on it.