06 Cooper S ..Revs up and down constantly at stop
 

Good day all,
I've had my S since 2012 and now have 200K miles and running. My current issue with it is that it acts as if I am pressing the accelerator at stops or while in nuetral. It is a manual transmission. It doesnt do this right away upon startup, but only after about 10 minutes of driving does it begin. all runs well but this is very annoying as I know it is not normal obviously. I am sure it is a sensor of sort but I just cannot seem to locate any info to assist me in this on the web...I do hope someone can assist..

I thank you all..