560 sl mercedes 1989 idle is too high-seems to be stuck

at rear of engine ,flywheel 5mm allen key or 10mm socket

gas or diesel..

Check fuel pump relay.
Check fuel pump control cirucuit.
Check fuel pump/

catalytic converter is clogged basically its stopping up your exhaust. Over time the pressure will slowly vent out, allowing your car to start, only to build up the backpressure again, stalling engine.

Classic example of a clogged catalytic converter! I bet it will restart after two hours as well.

Check fuses (for tachometer), fuel pump and blew through injectors: they can have some residue ice from gasoline

Could be breather tubes for emisions are dried and cracked,valve cover gaskets or a head gasket. The fix is to replace them.

The Idle Air Control valve is located on the throttle body. If you follow the intake tube from your air filter all the way back to the intake manifold, where the intake tube connects to is the throttle body. Remove the intake tubing and you can see the throttle body.

There are two sensors on the throttle body and a vacuum line. You'll see two harnesses going to the throttle body, one is the IAC.

However, a quick diagnostic check can be done without touching the throttle body to confirm your problem. If the car has a normal idle when initially started but then rises to a higher idle and stays there BUT then if you were to shut the car off and restart it and it comes back to normal that is the Throttle Position Sensor (TPS). This is also located on the throttle body (the other sensor to the IAC). If it is the IAC it will be high and maybe fluctuate a bit.

check air tube to idle control valve

There seems to be an intermittent electrical failure on the wiring from the radio to the power antenna.
Is this power antenna the original one?