Next time it does it take one of the spark plugs out and see if you have spark. If you don't have spark then you need to troubleshoot the ignition system starting with the plug wires and working your way back towards the distributor. If you get to the distributor with no problems then the ignition in the steering column. If you do have spark then I would start with the fuel system. The first thing to check would be the pressure to make sure their is no blocks or a faulty pump. good luck and maybe some others have a few ideas also.