I just purchased a CPO 1997 528iA a few weeks ago. When cruzing on smooth pavement at around 70-75 mph, my steering wheel vibrates. Is this normal? What I find weird is I notice it not on somewhat rough pavement, but only VERY smooth pavement. It's not very pronounced, but I am still noticable. Should I have the wheels balanced and/or aligned? The dealer says that all of this was done when the new tires were put on less than 500 miles ago.