quamosa

Every once and a while, maybe 25-50% of the time, when starting the CLS engine, the Parktronic sensors make a long beep, and show 4 red dots in both the front and the rear indicators. It seems to be an error of some sort, because the parking sensors deactivate when this happens and wont reactivate until you stop and start the engine again after a little driving. My mechanic didnt know what this meant and the dealer wanted me to drop it off and pay for service to troubleshoot. Does anyone here know what this alert means and how to prevent it? I wash the car every week so I don't think the sensors are dirty when this happens but how would I know? Its not consistent, so its hard to reproduce for my mechanic.