Radio/tape Cd Player problems of the 2014 Mercedes Benz CLA250

My class c 250 2014 vehicle. Diving long distances on the interstate started hearing loud static over the speaker system. The radio was not on. The noise turned into a loud screeching/ static noise from speakers with an electrical burning smell filling the car's cabin. I pulled off-highway, turned the car off, the noise/ burning smell did not stop. I let the car sit for about 1 hour. After the car was turned off for 1 hour, the noise /burning smell stopped. This has become an ongoing issue; I have taken my car to the mercedes dealership. They have stated it could be the "star service" electrical problem, but no guarantees; in my complaint, there were no rectifying of on issue. My fear is electrical fire, while traveling. I commute by interstate daily.