bas esp light
Same thing used to happen on my 02'. It was actually the brake sensor wearing out that caused it. They tend to go out around 90,000 miles. When it blows out ABS, ESP, and cruise control go offline. You also lose your brake lights. Mine was intermittent for about 8,000 miles before completely dying. The part costs $20 and is pretty easy to fix.
there is a recal for ml 320 for brake swittch. Brake sensor is another one.
Search Mercedes-Benz M-Class Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Mercedes-Benz M-Class Experts