I just leased a new X5 and since I picked it up I feel a shimmering/vibration mostly in the seat at higher speeds. It seems to come and go but is mostly there. I brought it in to the dealer and they found that 2 of the run flat tires had flat spots. They replace them, checked the balance on the other 2 and said they were fine. The two new tires didn't solve the problem. In fact, it didn't even make it better. I only have 700 miles on it and can't believe a vehicle at this price will have this bad of a ride. I ordered it so it was manufactured in April and hasn't sat on a lot for an extended period of time. Any ideas?