You need to pull codes to verify, but typically, it's a faulty brake switch.

The same issue cropped up on my 01 CLK and a 99 ML320 I formerly owned...the switch replacement corrected the problem.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car