Front suspension
 

I am new to the forum and hope to learn all I can from the people that own and drive these cars. I just bought a 2002 S430 and am going over every item to check it all out. Each time I turn it on I always get the "No faults found" which is reassuring. However, after sitting over night, the front has dropped about as far as , I think, it can go. The rear has dropped some, but not as much as the front. When I start it, it gives me a message,"car too low, don't drive" or something to that effect. As the car sits in idle, it starts raising and in a min, the message goes out and the car is level. It will stay level all day and does fine.
I don't think this is normal and would like to find out what would cause this?
It must be a leak some where but how does one start looking for the leak?

I'm going to go on a limb and assume you do not have ABC. If that's the case, you have a fault with the air suspension, most likely a front strut. Does one side of the front seem lower than the other? I know for Audi's a leaky strut leads to a burnt out compressor from trying to keep up with it.

The leak is found by spraying soapy water on the struts and air lines

It may not necessarily be an external leak it might be a valve block leak that internally releases the pressure

The compressor and valve block are in the right front wheel well, the reservoir in the left front. Plastic lines run from the valve block to the struts. The lines to the front struts are visible when you open the hood. The lines to the rear struts are under pop-off covers on the rear package shelf (inside, under the ends of the rear window).

One of the more common leaks is the diaphragm in one of the struts. Usual fix is to buy lifetime-warranted rebuilt struts from Arnott, or try to find good used ones.

This might give you more info on how the system works.
https://w220.ee/Airmatic