A squeak from the steering column is often related to a rubber boot in the column or a seal in the power steering rack.
Car Problem Reports
Mercedes-Benz E300 Squeak in Steering Column Due to Rubber Boot or Seal
Mercedes-Benz E300 Problem
Visitor, 1999 Mercedes-Benz E300, 75,000 mi
Slight squeek in the steering column. Dealer suggested a synthetic power steering fluid replacement for $169 as a way to correct this. The alternative is a $1,500 steering column. This is related to the bushings getting old. Bill