My car will seemingly randomly begin to rev upwards of 3000 rpm while at idle (manual transmission) after a brief period of driving. Shutting down the vehicle and quickly restarting corrects it at least for awhile. This has been an ongoing problem for over a year and I believe it is now happening more often and to a higher rpm. There is no check or service engine light coming on. My car has roughly 84,000 miles. Has anyone experienced this before? Any info. would be greatly appreciated. Thanks.