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

[amyandmark3]

Humtech, there is a highway (I-69) within a few miles of the Carmax where the speed limit is 65 mph. The shake is in the seat. It is pretty non-existent up until 60 mph, is at it's worst between 65-70 mph, and isn't quite as bad at 75 mph. We don't drive over 75 mph, and generally stay in the 65-70 mph range. We do have a highway by our house (I-74) where the speed limit is 70 mph, so these speeds are pretty common for us, have never had any police issues for going 70-75 mph. BTW, no shake during braking.