Moon187

I own a 2006 E500. I just recently noticed that when I'm at a red light for instance with my foot on the brake, I can hear a clicking noise coming from the back right side of the car. It sounds like the clicking is coming from the trunk. It makes this clicking noise about every 3-5 seconds while foot is on brake. This is the only time I hear this clicking noise. If the radio is on I can't hear it. However if radio is off and my foot is pressing on the brake there is a faint clicking noise only on the back right side. Any ideas guys? I'd appreciate any feedback. Thanks!