I checked the archives but every answer point to fuel system not keeping its pressure for a cold start. My 1990 535i always start perfectly when engine is cold (overnight or after a day at the office)so i figure that the injection system is keeping its pressure. When hot it will restart only after a long crank or perfectly on second crank after a short first try. Could it be related to a sensor or any other electrical problem, if so, your advise on what to look for would be appreciated.