[1JB]

Take it in. Who know what it is for sure but they will figure it out if they're half as good as the service department at my dealer. My '06 had an intermittent squeaking sound that seemed to come from inside the car but that I also noticed with the top down. It did not go away after driving for a period and occured with a slight undulation in the road, particularly on the highway. They took the car for 2 days and were able to duplicate the noise. They isolated it to the rear suspension with some sort of directional microphone but couldn't duplicate it in the shop. They replaced 2 parts of the rear suspension and finally cured it by replacing the right rear strut.