Vehicle will not complete drive cycle for emissions

Once readiness monitors are complete and vehicle is placed in park the engine will shut off. There is no stuttering or bad running, it just shuts off. When restarted the monitors catalyst, o2, o2 heater, and evap are all reset to incomplete. Drive cycle counter is also reset. Cold soak is performed for another attempt at completing monitors and again after completed same shut off at idle happens restarting the problem. Shut off happens hot or cold and intermittent but only at idle never while driving.