The early versions of the central gateway module (which allows different systems to communicate with each other) have software problems.
Car Problem Reports
Mercedes-Benz E350 4MATIC Early Versions of Central Gateway Module Have Software Problems
Mercedes-Benz E350 4MATIC Problem
Visitor, 2006 Mercedes-Benz E350 4MATIC, 82,000 mi
I had the same problem . interior light dim automatically, AC turns on and off automatically, and brake check engine lights turn on and off and show display malfunction. I had to take it to the dealer and found that the central gateway module part # 1695406945 has corrosion and warranty doesn't cover. Part price was around 180$ and labor is 800$ .. what a big crappy dealer here in San Juan Tx.