My '98 ML320 started playing with BAS/ESP light in ...1998.
First the game happened on summer together with an 'emergency attitude' of trasmission (you can use 1st gear only):you can imagine how happy on the highways! finally dealer solved it with substitution of the 'low gear actuator' that cost me a fortune (later somebody told me was an origin problem solved by Mb under warranty)
Anyway after 6 month...again and again till now. The only solution dealer found during these years was ..reset the controller! ...but now after 6 years and no more warranty they say I have to change BAS/ESP controller (estimate cost in Italy is almost 2k$!!).
What i found strange is that every year the game start on late spring ending on fall and even now nothing happen when is cold (at 25° F BAS/ESP works perfectly!). This make me even more doubtful on the controller.
Any help will be much appreciated.