BMW Repair: starter rolls, but engine does not start, neutral safety switch, bmw 535i

Question
i have a 1988; BMW 535i. I was driving it and it just went off. I tried to start it again, and it kept rolling i.e the ignition but the engine did not start. I havent done any major tune ups recently, just an oil change. before that when i try to start it the ignition clicks, and also the transmission slips occasionally when on high speed. it seems the transmission line is rusty therefore it leaks, transmission fluid, fast. what could be the problem.

Answer
sounds like you have more than one major problem.  do you mean it cranked without starting? or the ignition works but it won't crank.  the clicking you hear is the relay for the starter, either the neutral safety switch is fucked or a relay or wire to the starter is missing/shourted out.  try and start it in neutral.  if all else fails, jump the terminals on the relay for the starter to be sure the starter or solenoid is not the problem.
change the line on the transmission to prevent future leaking.
-cheers