Do something like this :
create a trigger that will be activated by the event that will make your vehicle stop and put "dostop nameofmyvehicle" in the activation field. Your vehicle will turn off its engine after a few seconds.
To get it moving again, use another trigger, with whatever condition you need, and put "nameofmyvehicle domove getwppos [nameofmyvehicle, x]", where x is the number of the next waypoint you want your vehicle to go.
Is that clear enough ?
Don't forget to remove the " " in your line of command !