OR another thing might be, if you have some water in your fuel tank, the water is heaver than the fuel and if you're on an incline, the water could be at the back edge where the fuel line comes in from the pump and it might be sucking bad fuel that could stahl the engine and make it difficult to start again. Kind of out there, but could happen. Where do you get your fuel from? You might want to switch stations and see if it goes away.