general problems of the 2007 Mercedes Benz R350

I had to take the vehicle to the shop for repairs at least every 3-5 months since the day I bought it, which was in 2010. Nearly all of the repairs have been under warranty, it only has lessthan 75, 000m. In September of this year while I was driving home from work when the care started staling jerking and shout off. The engine light, esp light and the break light came on. It immediately restarted, the engine light stayed on, while the esp and break light went off. This was a very frighten experience, hoping I won't be hit from behind. I made it to the dealer ship. The car was in the shop for 3wks when I was told that it needed to have a tune up before any other repairs could be done, how this related to the vehicle just stopping in mid drive, is odd. To say the least. 2 days after getting the tune up, it is still in the shop because the engine light is still coming on. I'm feeling uncomfortable about getting behind the wheels again in this vehicle. I expected more out of a mercedes bens with less than 100,000miles.