So i has the car all serviced and all was working well until one day I went to put my foot down and the car red lines and dident go into second until I let the accelerator off and now I’m first gear don’t change gear till the revs are lest 3k I’m not to sure what’s wrong with it it’s a 2005 MERCEDES c36 amg need help on what it could be I got told it might be the plug that goes into accelerator pedal ??