2000 Beetle AC Problem

Our 2000 Beetle has a strange problem when running the AC. If the car is running while sitting still either in park, or stopped in traffic or at a traffic light, the car experiences a loud series of "clicks" that almost sound like the compressor going on and off. It also experiences a definite vibration while it makes this sound. The clicking sound and vibration stops as soon as you begin moving again. This only happens while the AC is on. Otherwise the AC unit works well.
Any advice would be extremely appreciated.
Thank you!

My 2000 Beetle had an intermittant problem with the AC. Turned out to be the 30 amp fuse holder located on top of the battery cover. Maybe corrosion caused a poor contact, but the holder began to distort. When this fuse is out, the fans & AC stop working! It was an easy fix. My holder just needed some contact cleaner and a new fuse (the old one was "fused" on one prong, so it broke on removal).
Cheers Eric