I am sure this is a common problem. I looked through most of the W123 forum threads and I don't see anything that addresses my theory. Here is the scoop: When it is warm outside (above 90 degrees F or so, which is very common here in Arizona) and I drive my 1981 240D until it reaches operating temperatures, it will not start after being shut off. I have to wait an hour or so for the engine to cool down before it will start again. When it is hot, it makes no sound or attempt to start. When it is cold outside, it is not an issue. When I purchased the car, it came with a glovebox full of maintenance papers from the dealer. In 1985 the original owner took the car to the dealer complaining of the same issue. The dealer removed the starter and bench-tested it and determined the starter was fine, so they reinstalled it. Most of you already know the starter is mere inches away from the exhaust manifold. You also know the solenoid is mounted on the starter. Is there any way the proximity of the starter to the exhaust manifold causes the car to not start? Perhaps there is a temperature switch that overrides the starter when it is hot? If so, can the solenoid be moved to the fenderwell? Most other manufacturers put the solenoid on the fenderwell or firewall.