rpm fluctuation on 1999 Saab 9-5

When stopped at a light,rpm jump up to 11,000 rpm and back down again to 9000rpm causing a jerking motion. When in N its ok and it runs good. Also does this offen in reverse. does not do this all the time but becoming more frequent

Asked by for the 1999 Saab 9-5
Did you find out what was causing this problem? Was the engine speed really jumping up that high?