I have a 2011 E350 non-4matic with 42,000 miles. Aside from a slight knock coming from somewhere underneath the car when going over a slight bump with only one side of the car, or even a speed bump, the car is terrific! When parking at an outdoor event recently, we had to drive across a grassy area and I'd hear/feel the knocking, sometimes in quick succession, any time I'd encounter a dip or bump on one side of the car. Anyway, I digress.

The only other concern I have that's giving me pause is a very slight vibration or buzzing sensation coming from the steering wheel, particularly at speed. This sensation subsides when I release the accelerator. For example, with the cruise set at 72mph, if I encounter an incline and the rpms increase to keep pace, I'll feel this sensation, but more pronounced. Once I top the hill and coast down the other side, the sensation goes away until the engine has to start pushing again. Keep in mind, the steering wheel is not bouncing back and forth as it would with an out-of-balance wheel/tire. This is definitely RPM dependent and sometimes makes my hands feel numb after driving 30-40 min on the highway....nothing ridiculous, but enough to make me think, "Is this something I should have checked out?" There's no alarming shake at idle, in or out of gear. There's only a slight vibration once I place the car in reverse or drive, but I've attributed that to simple driveline vibration.

I've read people from the ML forums discussing this and some found it to be a characteristic of their vehicle. I'm wondering if my engine or transmission mounts could need replacing, even though the car has very low miles. Keep in mind, this is my 6th Mercedes and third E-class and I just don't recall this with my other vehicles. Any thoughts on what this might be, or am I being hypersensitive? Thanks in advance!