I owned an ML 350 petrol 2008 model. I sold it on 200 000km and I now have a ML 63 AMG with 190 000km. Funnily enough, on both cars I also experienced the same problem, which is more noticeable when cold.
My two cents’ worth is that these vehicles are quite heavy − approximately 2.3 tons – and when the car is left standing overnight, the tyres do tend to get flat-spotted on that part of rubber.
So, when you get going, it vibrates ever so slightly till the rubber is warm, after which you don’t feel the vibration that much.
It’s important to note that the mags do tend to buckle if you hit a speed hump or pothole, so it’s worth checking this when you do your wheel alignment and tyre balancing (every 10 000km).
I have two spare mags in my garage as I often have to send a mag for repair, and I frequently travel up to 5000km a month between Joburg and Swaziland.
I would like to hear if anyone else has had this problem, and how it was solved.