Your car has a headlight relay... they all do. I have a 1985 745t and I have a headlight relay. The 1985 layout is a little different than everyone else's for some reason (1 or 2 relays differently laid out, and the locking relay is in the driver's door on the lock switch rather than the relay board), but the headlight relay is there.

The lights are generally in the front row of teh relay board. Turn on the lights and start pulling the front relays until the headlights go out. That's your headlight relay... should be a 2x12v small, square, silver relay.

This is almost undoubtedly a relay issue. If it isn't, it may be that your headlight switch is shot. BTW, MAKE SURE you replace the relay with EXACTLY the same one. Many relays look EXACTLY like that relay but can be differently designed. Your headlight relay has two pathways (hence the 2x part of the description) and must be replaced by one with the same logic capabilty.

good luck,
rt