Have you changed your tires recently ? Usually the first most common cause of vibration is unbalanced tires, especially on big diameter wheels like 21" or 22". Try to find any local shop that has RoadForce Hunter 9700 balancing machine and balance your tires ( with roadforce option).hi friend
I have an l405 2015
today as I drove on a highway a vibration starts over 50miles/hour and seems to be the same problem as the one you described.
I thought that are the tyres the issue which are almost new i move the front rear and opposite but still have the same problem.
did you solve it?