I tell you what it is...its the IAC valve. You need to remove the valve and clean it with some carb cleaner in the plunger area and around the spring, use a tooth brush and clean it the best you can...then apply a light spray of lubricant like wd40 or something. It usually clears up any idle and surging idle problems. If you never done a throttle body cleaning you could do that as well. All this info can be found by searching IAC and throttle body.
