About 2 months ago, I purchased a CPO 2015 C300 and after about 2 weeks, it started to have issues. Between 2nd and 3rd gear it would shift really rough and sometimes it will jerk the car violently like it's stalled. I've taken it into the dealer 3 times now for the same issue. They did a software update (car is still under warranty) on the tranny but same problem. This issue is annoying but whatever.

Tonight, another issue occured. While driving at about 35-45 mph, the car was very hesitant to accelerate and was making weird noises. I really thought I had a flat tire of something the entire car was rattling. I attached a video and in the beginning, you can see the rpm is at about 3k and I'm going about 40 mph and the car was not accelerating. At the 12 second mark, I had let off the gas and tried to press the gas again and the entire cabin was rattling. It sounds like that it's coming from the engine but it's the sound of the car shaking. So damn weird.

The Mercedes dealer probably thinks I'm crazy at this point because they've never even acknowledged that my car has any issue. If somebody could watch the video and maybe decipher a possible reason for the issue(s), I would really appreciate it. I know absolutely nothing about cars...lol.

Update 9/7/18:
Just spoke with my service advisor who told me they ordered a speed sensor which they will put in tomorrow. I looked up the common issues with a failed speed sensor and based on that, I don’t think that’s the cause. I’ll update tomorrow after they replace the part.

Update 9/8/18:
I picked up my car today and my service advisor told me they took it on two 10 mile test drives (a few hours in between) and the car was running fine. After I drove it a bit, the rough shift between 2nd and 3rd gear was still there (no surprise) but no issues accelerating or crazy noises. I'm just going to live with the tranny shifting issue because it's obvious the dealer has no interest in trying to fix it. I may go to another service center like BH or Calabasas in the future and see if they can figure out the issue that Mercedes of South Bay cannot.

Yes I took the car back to the dealer this morning and showed my usual service advisor the video. She seemed to be shocked at the sound so I’m hoping this time around it will be repaired properly. We will see, I’ll make an update when I hear from her.

I took the car back to the dealer this morning. If the issue isn’t solved this time around I will call Customer Care. Thank you so much for the info!