2012 BMW 535xi shakes at 50 mph when braking
If you've had both sets of rotors replaced, then I will assume the brakes are not the problem. Other issues that would cause the problem you are having include worn wheel bearings (https://www.yourmechanic.com/services/wheel-bearings-replacement), worn steering or suspension parts (https://www.yourmechanic.com/services/brakes-steering-and-suspension-system-inspection), or...