I can't figure out what is going on -- any ideas?

[VertheinMD]

Just got back from the wheel shop and they tell me my balance is perfect and my 4-month-old Michelins look fine. There goes the cheap answer. Before I give the car over to my shop for an expensive Easter egg hunt, I was wondering if anybody had any guesses about what could be causing the following problem: A few miles into my drive my front end starts to sound like a tank, like I have major flat spots on my tires or something is wobbling around. There isn’t a noticeable pull on the car, but there is some vibration. After another mile or two the problem disappears and I’m back to a smooth ride. I thought that my calipers might not be releasing properly once the car heats up, but that doesn’t explain the sudden onset of the problem while highway driving (no brake use). I thought a bad wheel bearing could be the problem, but I don’t hear a whine, and I don’t know why the problem would fade after a few miles. I’ve never heard of a tire that is fine cold, warps as it heats, then is fine hot, so I can’t imagine a tire defect. I’m stumped. Any ideas?

[m_power]