Why does my 2007 Volkswagen G.T.I. not idle correctly when I am sitting still. on 2007 Volkswagen GTI

The tachometer jumps up and down while sitting still, from 10 to 30.

Asked by for the 2007 Volkswagen GTI
scan codes to see if there are any then post
1 more answer
review when last tuned. may be problem with ignition system. bring to shop for diagnostic to find out for sure.