Why is it jerking when I let off the gas? Please help

Why is it jerking when I let off the gas? Please help I have a 99 jeep grand cherokee with a 4.7 L v8 every know and then it will jerk or stall when I take my foot on the gas then If i press on the gas right after it has a jerk again but shifts smooth? CAN SOMEONE PLEASE PLEASE HELP I AM VERY LOST THANK YOU SO MUCH