Try thoroughly cleaning the inside of your throttle body with a can of aerosol throttle body cleaner. The IAC (idle air controller) that feeds all of the engine's air into the engine at idle when you're not stepping on the gas might be sticking and not letting enough air into the engine at idle. The IAC is bolted onto the passenger-side of the throttle body and it gets its air for the engine through the slot on top of the throttle body's butterfly valve plate that is closed at idle. Make sure some of the cleaner gets into that slot (idle air control passage inlet) as you can see in the below illustration. The engine needs to be running while you do this, simply hold the rpms up a tad while you spray into the throttle body. Complete instructions will be on the back of the can.