What shape is the battery & it's connections in? I was working on my 89 760 and had the battery out to charge it. I plopped the it back and and slipped the cables back on, but didn't snug them up really well. I thought they were on pretty well, but they would still slide around if pushed. There are 2 wires on the (+) side, and when I wiggled the smaller of the two, the car cut out, but would fire right back up. It's symptoms mimiced a lot of other well known issues (various relays, hall effect sensors, etc) . Maybe even check the other end of the wires. Clean them up really well and give them a coat of dielectric grease or something.