Most of the time the CE light is an indication of a smog-related problem, like the O2 sensor. The car will run fine otherwise.
The engine management system has the ability to adjust the mixture within defined parameters, so it can mask the problem. Once the adjustments reach the limits of the parameters, it can no longer compensate, and the light will eventually come back on again.
I'm no expert, so at the very least, take it to a shop that can pull the codes. If no codes, then press on...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car