R56 Stalling
 

My Mini from time to time will stall while driving. Pull over to the side of road and let sit for about 5 minutes and it will restart. Changed fuel pump relay and solved problem for about a month and now doing same thing again. Took to local Mini dealer and they cannot find a problem and no fault codes stored in computer and they have no idea what is wrong. Anyone else had this problem and what was the remedy?