Every so often, maybe once a week or less (but always at the most inconvenient time) my 1987 740 turbo wagon will not start. There is enough charge in the battery to run the lights, door chimes, radio etc but not enough to turn the starter. If I put jumper cables to it, it starts immediately and gives me no more problems until the next incident, maybe a week or a couple of days later. The problem is so (seemingly) random I'm not sure where to start. Failing brush/diode pack in my alternator, intermitent electrical short somewhere? I've been trying to watch the voltmeter for evidence of poor charging just before I shut the car down, or maybe figuring out a patern of witch electrical accessory (lights, power windows etc.) I used just before the problem occurs, but haven't come up with anything. It's very FRUSTRATING!!! Please help before I start needlessly tearing stuff apart or WORSE wind up taking it to a shop.