I've always experienced this every time I drive over uneven roads. The rattles are however a bit muffled when I have a golf bag or any sort of heavy item in my trunk. Has anyone else experienced? If so, how did you fix it?

 

If weight in the trunk helps I would see if the spare and tools are all properly situated under the trunk mat.

 

I experienced the same problem. Drove me crazy. It sounding like it was coming from the trunk area when in reality it was coming from above and behind me.
I took car in to the dealership and they clearly heard the noise. Said it was something loose in the sun roof. They fixed it and the noise has not returned.

 

so that's where it was coming from... thanks a lot! I'll bring it to the dealer to have it fixed

 

Yep, It is a sunroof issue. I had that too. Dealer replaced my rubber surround of the sunroof glass and tightened things up and rattles (and wind noise) was fixed.