my 1990 525i has had better days. the other day i go to start it and it won't turn over. i go and hit the starter to see if it siezed up but that wasnt the case since i had a mechanic some and start the car by hot wiring the starter with the key in the in position. i tried starting the car with the key again and no crank. the mechanic did the starter method and the car cranked for a bit then started up. he said it's a sensor in my ignition?

and ideas? i'm lost.

note: i never had to press the clutch pedal to start the car. it always did without that.