stopped at a stop light or stop sign or sitting with it idling it acts as if it wants to die?

I have a 2004 chevy cavalier that runs fine like on the freeway and when I am just driving but whenever I am stopped at a stop light or stop sign or sitting with it idling it acts as if it wants to die the lights go dim and it sputters like it is going to die. Just wondering if you could tell me what could be wrong with the cat.