I had something similar but when I was driving. Turned out to be a faulty rear hatch latch that was fixed for free under a Crossfire technical service bulletin. If you haven't tried it yet, wouldn't hurt to go to your Chrysler Dealership, according to the TSB, all it takes is a customer complaint of the sound and they will replace the latch. If that doesn't take care of it you'll know to look deeper.

Good luck,

Ruzo