Cars that tend to wander at highway speeds are out of alignment(or were & the tires are worn). Wandering comes from incorrect CASTER & or toe-in settings On the front end, or incorrect thrust-angle & or toe-in on the rear end. Have whoever did the alignment recheck the alignment & ask for a PRINT-OUT of the finished alignment. I've noticed that the W210 chassis is prone to slight drift to the right. Perfect alignment can help this problem.