Check in your owners manual. I think the blinking light is an indicator that the fuel cap is not sealing properly. If you replace the cap be sure to get a real Mercedes cap to insure proper operation. The evaporative emissions system on your car performs periodic leak tests on the fuel tank which is probably why the light is coming on. If it continues to happen it will set a code and turn the check engine light on.

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Mercedes Benz Master Tech - Retired