How many miles do you have on it? Take it to the dealer AFTER your warranty expires...they'll find all kinds of stuff wrong with it. Haha. my hummer dealer which I happen to like never found anything wrong with my truck when it was under warranty, I always had to point everything out to them. Then at 51000 miles I had a cracked radiator(I found that) and leaky water pump. I guarantee it happened before 50k, and my h3 was there numerous times from 40-50k.
Anyway, about the tire vibration...is your truck aligned? Do you maybe have a bad shock?...cupped tires?...I had all of the above at 40k and it drove like you describe.
Also, has it been leveled? make sure your suspension up front is dialed in correctly. Good luck.