The flickering light indicates that there is something wrong with the charging system. IE, the alternator or battery. The simplest thing to eliminate first is the battery. Get it tested for free. Then if it is bad replace it.

Also another simple thing to check is the belts on the alternator. They may be slipping and or loose.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD