Check Engine Light On problems of the 2014 Mercedes Benz C250

I leased my vehicle in November of 2013. The vehicle is driven to and from work and in the beginning I never had a problem. A few months ago I was driving down the freeway at 70 mph and all of a sudden the check engine light came on and the vehicle lost power. The vehile would violently shake whe trying to accelerate. I manged to continue to drive for about another 30 minutes and made it to the dealer and turned the car off but once they restarted it the car ran fine. Since then then car will randomly loose power all of a sudden it has been to the dealer 3 or 4 times and they keep it for a week and then give it back and say that they were not able to recreate the issue. I have almost been hit once so far and when I let my brother use the car he was almost hit while making a left turn because of the random power loss. I have contacted mbusa and spoke with someone named juan. I continued to call him ans take the vehicle to the dealer everytime it happened expressing my concerns abiut the car as well as safety. Juan intiallly acted as if he cared but that was shor lived as he finally called back on 10/2/15 and explained that his managers and mbusa were unable to create the issue at the dealer level so there is nothing they will do at this point. . . At that point I realized that there is nothing that mbusa will do for me and that I will continue to forced to drive and pay for a very unsafe vehicle.