Just Is

Had my transmission flushed and an oil change done yesterday on my clk430. All seemed to be well when I picked it up but then last night I started it up, for the second time after getting it back, and it revved all the way up to about 2100 rpms instead the usual 1100. also after driving for a bit and going back into park it sits at about 1100 rpms whereas it used to be at about 800. any ideas?