Perhaps check witht he charging system.
Check the brushes int he alternator if it has them, and if they are very short, replace them.
Take it to you local auto store that does repairs, and have them test the charging system.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.