There need not be an unbalanced force acting on a moving object. If an object moves with a constant velocity, there are no unbalanced forces acting on the object.
Objects continue in a state of rest OR UNIFORM MOTION , unless an unbalanced force acts on them . ( Newton's First Law of Motion ).
Things that are moving, just keep on moving. They don't need forces to keep them moving.
But if there is some force ( such as friction ) that slows them down, then they need another force to make them get back the speed they are losing.