Next time your car doesn't start try opening and shutting your doors. If the car starts after doing this, check to make sure the door jam switches are not stuck in the door closed position. If they are stuck on one side or the other it could be messing with the alarm module. It will give the symptoms of a bad crank sensor and you'll have no spark and no fuel. Which this wont help you if your car doesn't have a factory alarm. I had an intermittent no start on my S2 for the first 3 years I owned it and I just happened to check this and the door jamb switch on the passenger side was stuck in the door closed position and was messing with the alarm. Also you can try the alarm bypassing procedure on clarkes-garage.com.
