There are 3 common causes for this. 1 a failing crank shaftposition sensor, 2 a failing cam shaft position sensor, and 3 a failing PCM(engine computer). Either one can act up when the engine warms up I have seen some issues where a cam or crank sensor will fail and not set a code. But try this the next time it acts up: crank the engine for at least 15 seconds and then recheck for a cam or crank sensor code. If there are no codes at all, thensuspect a failing PCM and have it replaced. Most auto parts stores will connecttheir scan tool for no charge to you.
Hope this information helps, and let me know if you need moreassistance with this.