when i start my 03 civic ex 1.7 vtech idles rough an almost stalls

What is your question?

when i start the car it starts idle normal at about 1000rpms an then starts to idle rough an goes to like 500rpms an almost stalls for like 30 secs then comes back to normal an somtimes when u start driving at like a stop light or etc.. it starts off putting like its going to stall then goes fine what could be the problem?