2004 Vauxhall Corsa revs on its own.

I was driving down the road and as i came to a junction to stop, my car started reving its self. it reved to about 3000 rpm and stayed there then the service light came on. i pulled over and turned off the engine then turned it back on and it done it again. i then turned it back off and left it for about 5 mins and tried again and it worked fine untill i got home. i left it for a few hours before turning on the engine again but when i did it done the same thing again reving to about 3000 rpm, i have never seen this happen before and i have had no other problems with the car.