That seems like your IAC valve is starting to go or it's getting clogged up. Fairly common on our 6GAs. Remove the IAC valve, clean it up, and let the car reprogram itself to the clean IAC valve (about 50 mile drive or so) and see if it keeps happening. If it does, then replace the IAC valve as the sensors inside of it may have failed and do the re-program thing over again.