I get the shake between 70 and 80 MPH. Took it to the dealer for that and steering wheel judder while braking.
I only had 72 miles on it. They had to resurface a rear rotor. That got rid of the steering wheel judder while braking.
Still have the shake....They say they don't feel anything and to drive it to 1500 miles and maybe it will go away on it's own.
I am going to bring it back next week. If you drive at 80MPH you can see the passenger seat shaking pretty good.