I've had this problem before and am somewhat concerned. Before when I had this problem the "check engine" light and "washer fluid" light came on. I needed washer fluid so i put it in and that light came off. I brought it to the mercedes dealer and after I got it back the "check engine" light was off. About week later the "check engine" light comes back on and I've been driving it fine ever since for about a month. Should I be concerned? It really bothers me and now I'm scared to accelerate fast.