See also:

Deactivating HDC
Press the button again and the LED goes out. HDC is automatically deactivated above approx. 37 mph/60 km/h. ...

Distance to back of head: electrical head restraints
The head restraint is automatically repositioned when the shoulder support is adjusted. ...

Automatic deactivation during forward travel
The system switches off when a certain driving distance or speed is exceeded. Switch the system back on if necessary. ...