intermittent problem 81-380SL

I have an intermittent problem with my 81- 380SL. I have seen 3 symptoms that might be related. 1). While idling cold, the idle speed will suddenly increase to about 2000 RPM. 2) Engine stalls at traffic lights when both hot and cold. 3) When warm , engine will go to about 2500 RPM with no warning. I have to be ready on the brake