my batery light on my 1997 mercedes sl500 flashes on for a few seconds

I would start by checking the condition of the belt. it may be slipping causing the alternator to spin slower than normal. A slipping belt will usually but not always make a squeling or chirping sound. If the belt is in good shape check for any defective wires on alternator. If all seems fine then it is probably time to have the alternator tested. You can perform this test by using a volt meter on the battery post. The alternator should be putting out 13.5-14.5 volts. If not it is time for a replacement. Many auto parts stores can do a check of the alternator while it is on the car for free.