Join Date: Jan 2017
Location: British Columbia, Canada
Try changing the drive mode to Sport or Sport + which changes the damping settings of the steering system. If the vibration is reduced or goes away, then it is probably software related.
I had a similar but different problem with my 2017 GLC 300 where the steering wheel vibrated continuously at speeds above 95 Km/h whether I hit bumps or not. I never experienced a front end shutter. If, while the vibration was occurring, I changed the drive mode from Comfort to Sport or Sport +, the vibration went away. If I switched it back to Comfort, the vibration came back.
I went for a test drive with the shop foreman from my local dealer. He mentioned there is a known issue where an oscillation occurs in the steering rack when hitting bumps at highway speed and the oscillation causes a steering wheel vibration and can cause the front end to shutter. He said there is a software update for the steering system that prevents the oscillation from occurring.
They installed the update on mine which significantly reduced the vibration. Then I reduced the tire pressures from an over inflated 38 psi to the proper 32 psi and now the vibration is totally gone.