Serpentine belt whining noise?

[Ploowah]

So every time I start up my car, my belt has huge deep whining noise for about 20 minutes, then it goes away. It also whines when I turn left or right, or hit the brake pedal. I could hear it when the car idles as well. Any experts able to guess the problem before I go to a mechanic?

Car: 2001 Mercedes C240

[CountryBoy]

Serpentine belts should be replaced religiously every 60,000 miles. At the same time the belt is replaced the belt tensioner mechanism should be insepected. If the pulley bushing on the tensioner or spring inside the arm is weak, a brand new belt will squeal for a time after start-up. The reason this happens is the alternator is bore difficult to spin because is re-charging voltage the battery (because of the start-up) and furnishing amperage to all the car electrical systems.

[whatawaste]

belt is slipping. could be an old stretched belt or could need tensioner pulley adjusted