Wheel balance. Defective tyre - can happen to one straight from the factory. The best shops have a machine that will check side wall flex and tyre pull as well as balance. Wheel alignment not so likely in this case IMO. +1 on checking other components though.
Good - Fast - Cheap: Pick any two.
E23 735i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E30 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i