On my 2012 GT the vibration seems to intensify based on whether I am drifting toward the lane markings with my blinker on, are on them or have crossed them. I tested during lunch.

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2012 535i xdrive

Alpine White
Black Dakota Leather
Cold Weather Package
Driver Assistance Package
M Sport Package
Premium Sound Package
Value Package
Sport Package
Side and Top View Cameras
Smartphone Integration