my 2010 se with 50k miles had a vibration which was quite pronounced at speed and sometimes when maintaining the speed steady at around 70, the vibration would disappear then return a few seconds later even worse then go and then return, perhaps cycling every 2 to 3 seconds. at its peak, the arm rest on passenger seat vibrated side to side about half an inch!

read up some threads on here and decided to get the fronts balanced & inspection showed one wheel had lost one of its weights so that seemed like it would be the answer. balancing didn't help so i took the car back and asked them to check the front wheels again and also do the rears.

on the balancing machine a slight (about 2mm) side to side movement could be seen on two of the wheels (both fronts) but the bloke said that was nothing to worry about, not uncommon and they were balancing up ok. it was clear that those two with the slight wobble required far more balance weights on them than the rears which had no side to side wobble.

whilst the balancing machine may well balance them up ok, when they were on the car i think what was happening was that given that the outside diameters of the two fronts would not be exactly them same, the car would effectively be trying to move side to side when the cycling or the front wheel distortion of the wheels syncronised every couple of seconds.

none of the wheels have any dings, dents or marks of any kind and we experimentally re-fitted one of the distorted wheels onto the balancing machine to look at it again. the 2mm distortion seemed to 'smooth' as in revolved, there was no flat spots, and the easiest conclusion to draw was that wheel mounting face was not in the same plane as the rest of the wheel - in other words that they were manufactured like this. sound unlikely i know but cant really see another explanation.

fitted the previously unused spare so now have 3 perfect wheels and one with a 2mm distortion fitted to the rear axle and the car drives perfectly.

incidentally, my car has deployable steps which are supposed to be removed for jacking but the Mercedes sprinter bottle jack allows jacking without step removal and, wrapped up in a very large rag, fits neatly in the corner of the spare wheel well that the original occupied - indispensable if you have these steps IMHO

Although yours is too young to have it, that type of wobble has been reported before and turned out to be a tie-rod end. Maybe you are unlucky and one of them went. Let your indie or dealer have a look and see if any of them are a bit too loose.

I have the MB jack as well, it's great (no deployable side steps, mine are fixed). MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!