Some convertible Mercedes-Benz vehicles have roll bars incorporated into the head restraints. In the event of an accident, the roll bar automatically raises and protects the vehicle occupants. Roll bars are particularly important in rollover type accidents. Whereas in a sedan, the roof structure protects occupants, a convertible does not have that, and therefore needs a roll bar. The retractable headrest-style roll bar allows for a more open driving experience than with a conventional fixed roll bar. If the roll bar deploys, it can need resetting.
Listen for the roll bar deploying, it will rise with a ratcheting-type sound automatically in an accident, or if the on-board computer senses a dangerous driving event taking place.
Press the upper half of the switch to reset the headrest roll bars on the Mercedes if they have been automatically deployed -- you will hear the mechanism engage. Then press the lower half of the switch to lower the roll bar.
Alternatively, if the roll bar was raised manually with the switch, it will automatically lower and reset when you press the switch to raise the soft-top.
Mercedes recommends that you raise the roll bar for safety reasons if the temperature is below five degrees Fahrenheit, or if the rear seats are occupied.
Check that there are no obstructions before operating the roll bar.