Mercedes ML 270 2004 stuck in limp home


After a minute of driving my ML 270 appears to drop into a safe mode where it accelerates very slowly, not to exceed 2000 rpm until it is in 5th gear. No matter which gear it is in, it will not exceed 3000 rpm.
This appears to be a computer "mode" that it gets into.
I understand that this is a common issue as a friend of mine has the same problem with the same car.