Originally Posted by sybarite

It would be helpful to know the year and model of your car, and whether it has the 'Eco' function.

On my '14 XFR-S, the 'Eco' function does exactly the same thing that you are describing, in addition to the usual 'Eco' operation at lights, in stop and go traffic etc. The difference between usual operation at a stop light, for example, is that it truly shuts off the car, including accessories like ventilation and the radio. It is intermittent because this function is only activated under certain conditions as determined by the ECU (for example, outside temperature, accessories running, level of charge). It is activated by firm brake pedal pressure, which is exactly what you apply when shifting the car into park.

The above may not apply to your situation, as it has nothing to do with how fast you turn the shift knob.