I have a 2001 Lumina with about 68,000 miles on it. Many times (but not every time) I turn the car on, it goes up to 1500-2500 RPMs, while in park. When I shift into drive, the car seems to drive itself without me having to give it gas. Usually after driving for a few minutes, if I turn off and restart the car while at a red light, it will be fine. This used to happen only occasionally but is happening more and more often. It's almost always in the afternoons after work, not in the mornings.
Another problem I have, occasionally the car has stalled on me when I am in stop-and-go traffic on the highway. It always starts up again fine right away. Happened a couple times last fall, didn't do it all winter, but did it again last week. Every time, it's been in the morning while I'm sitting in traffic on the highway.
I know absolutely nothing about cars, but even I know this must be a transmission problem? Any advice would be appreciated, thank you!