I love my BMW 330XI which has 170,000 currently. I have an recent issue... while driving at 55mph the car suddenly acted as if there were no gas. Sputtering I floored it and at least I was able to pull over to a safe place. I left the car and came back 2 hours later and it started right up with no hesitation... it had 1/2 tank of gas. This happened maybe 4 months ago as well. The car visited the mechanic then after being towed. He found nothing wrong saying it started right up. Please help me with any suggestions or advise me in what to check before I take it back to the mechanic. THANKS!!!