2003 Mercedes Benz ML350 Squeaky noise

The common suspects are worn control arm bushings. For some reason they used to easily last the life of the vehicle, but now every brand is having lots of problems. My guess is it's either the wimpy suspension designs or they're using softer rubber intentionally to create a more comfortable ride. Regardless, an inspection at a tire and alignment shop will identify the cause of the noise which likely is the cause of reduced handling. They also have a tool called the "Chassis Ear" to help locate noise sources. It's a set of six microphones, a switch box, and a set of head phones. They clip the microphones to suspect parts, then listen during a test drive.