High pitched "fax" squeal coming from car when off...sometimes hours later on 2006 Mercedes-Benz R350

I have heard of at least one other person with this identical problem but neither of us have an answer. After shutting off the car it will periodically emit a loud squeal from what sounds like the passenger side front engine area (almost a "fax machine" piercing sort of wheeeeeeeeee) and then stop. It will happen off and on without a pattern as to how frequently it recurs ...sometimes 4-5 hours after the car has been sitting. It is audible from a distance away from the car. The dealer has not been able to determine the problem.

Asked by for the 2006 Mercedes-Benz R350
you have the infamous airmatic suspension, similar to the one S-class MB owners have grown to hate. the MB dealers are simply warranty repair stations, as 90% of their customers leave after the warranty expires. my suggestion is to find a local MB specialty shop; ask
other MB owners who is the best.
There is no other local MB specialty shop that is reputable (to say the least). Is this something that is familiar and can you tell me what it is/what is causing this squeal? I have had no problems with the suspension system....unlike so, so, so many others.