Lee,
My does the same thing. Frankly its the most annoying thing I've ever had to go through with a car, New or Old. Mine is an 08 also. I've been back to the dealer 4 times, had a Lexus rep look at it, and all they do is try to defend their car. They did the tire replacement, and the balancing, but it didn't help at all. I'm going back once more to satisfy the lemon law and then get a lawyer. Mine does a couple other very annoying things too. I'll keep you posted.
SH