Does this always happend before traffic light or cross road when you stop to wait green light or stop sign. If so, then you have problem of hot idle, which usually comes from fuel mixture too rich. You need go to garage ask them do a tune-up, clean or the hose/cable iunder the hood. At same time, you need ask them to check any <<air leaking, fault sensors>>.
No, it is not serious problem but a hard to fix problem. Just like a bug in software. Technician needs to find out. Could be many times to visit the garage. Be patience and tell them exactly what,when this happens also ask them to test drive and reproduce the sympton.