I get a vibration on both sides of the roof right above the wind shied any else experience this? Nothing is loose. I'm thinking ill just fill the plastic trim with black silicone unless some one found a better solution. My 08 H3 had the same issue, maybe it's a Hummer thing. My current truck is a 05 H2T.

 

I had a noise that sounded like a vibration from the roof on the passenger side. I took off the windshield molding that goes up the side. Put some foam tape on it reinstalled it and it seems like the noise is gone you might want to give it a try

 

Long running issue, search is your best option. Remove the side windshield plastic, install new double sided sticky foam or whatever you want, reinstall.