Hi everyone. This site is awesome. Ive been lurking for a couple weeks now

Read thru the entire "hidden" features thread and learned a lot:
http://www.xoutpost.com/bmw-sav-forums/x5-e53-forum/23294-cool-hidden-features-e53-x5.html Im really happy i stumbled apon this place!
So... Quick intro. I live in the Kootenays of BC Canada. After driving Toyota and Mazda forever, Ive been wanting an X5 for a couple years now. Last weekend I flew down to Vancouver and picked this up for 5G
...and now, im in love.
Its an 2001 3.0i
Its the weirdest feeling to know im driving an SUV that handles better than my Celica or my MX3. In fact, it does EVERYTHING better. I will love this X5 for the rest of my life.
So here is the problem. The dealership I purchased from told me that one of the tires had a "flat spot" because it sat on them for so long, and if I had any vibration or shimmy on my way home not to worry - it would stop after the tire warmed up and I would need a wheel balance. Sure enough, about 30 minutes after leaving the lot with it, the shimmy started. I was on the freeway doing a buck-twenty-five. The steering wheel started shaking left and right and I felt a vibration through the seat. It continued for a minute and then stopped. After another 30 minutes passed, it happened again, but not as bad or for as long as the first time. I drove the rest of the 8 hour trip home without a problem. Ive been driving it an average of 2 hours a day at both city and hwy speeds since then and it has done it every day since. It doesn't happen when Im braking unless its already happening. I went in yesterday and had a balance done on all 4 wheels, and then this morning (cold) it was worse than ever. It was a violent shaking shimmy for 20 minutes while doing about 75kph. When I got to work I looked at all the tires and my front left was so hot I couldn't touch the rim. Then a few hours later I drove it back home (hwy - 45min) and it barely did it once and the tire didn't get hot.
Ive been searching online and on these boards and have learned it could be one of a hundred problems. Im reaching out to see if anyone else has had similar problems and knows what I should do. Why would it come and go like that? Would a flat spot on a tire cause it to heat up like that?