2003 Other Mercedes Benz Models Battery Warning Light

It sounds like your battery has a slow amperage draw from your vehicle. This problem is very common on 203 model C classes however I have seen this problem in other models. Your batteries amperage is being slowly drained from the vehicle when it is turned off. This is due to one of the many processors on the vehilce not turning off with the rest of the vehilce. The slow draw will eventually kill the battery. The reason your display has the battery warning when you get in is because of the low voltage and amperage in the battery from the time it has been sitting and draining. Once you drive a while the alternator will have fully recharged the battery. The problem will need to be properly diagnosed to locate the faulty processor and fix the problem.