07 H3 Shakes on highway at 65+ mph, normal?

[amyandmark3]

Hi, Hummer newbie here, sorry in advance for what is probably a dumb question.

We just bought a 2007 H3 with 57k miles. Very pleased with it except we notice that it shimmies/shakes a little once we get it above 65 mph or so. The tires are Good Year Wranglers and look to have about 1/2 of their life left. Is this a common characteristic of the H3's drive at higher speeds? Or should I complain to the dealer that we want this looked at / fixed? We just picked it up today and have no recent experience with 4 wheel drives, so not sure what to think. Thanks for any help and/or opinions.

Mark