I too have that annoying rattling sound. It' s on (or rather,
under), my '83 320i.
Don't think it's anything to do with the rear shocks. The rattling on my car seems more under the car itself. Like it's coming from under the rear seat.
Can hear it when i first start-up. During idle at signals and while getting up to speed. Seems to either stop - or is being drowned-out by traffic - when i get up over 45 - 50mph.
Almost sounds like some kind of metal plate has loosened and is rattling against something down there.
any ideas? thanks.