Due to tidal effects, the rotation of the natural satellites is expected to be synchronous with their revolution, i.e. they perform a whole rotation during a complete revolution around their parent planet. It corresponds to a dynamical equilibrium state, that involves that the satellite always shows the same side to its planet.
Cassini spacecraft has recently observed a slight super-synchronous rotation of Titan (+0.004%) and the authors interpret it as a signature of an internal ocean, that would dissociate the rotation of Titan’s crust from this of the core, justified by the fact that the motion of the crust would be sensitive to the energy exchanges with the atmosphere.
Another explanation is being proposed by researchers of the University of Namur (Belgium), the University of Lille 1 and Paris Observatory (IMCCE). Following Benoît Noyelles, Anne Lemaître and Alain Vienne, there could be a dynamical forcing of the angle (the wobble) between Titan’s rotation and pole axes, that could false the measurement of Titan’s spin rate if these axes were considered as equal.
Cassini space mission has been extended for at least two years, so more accurate measurements would allow to confirm or refine these explanations.