stalling at red lights

In the past two weeks my kia has randomly stalling at red lights. It doesn't stall at every red light and in the morning it doesn't stall at all. It is after the car has warmed up it stalls. When it stalls sometimes the oil light indicator comes on We had three oil changes March, Sept and Nov 2014. When the oil was changed all three times the oil was clear, no sludge or dirt particles were in the oil. What can be the cause of this problem