Hi Bhatt I have read with interest your post as I suffered a simalar problem
with my 1995 S420.Doing short trips and in my case not using the car every
day the battery failed to turn over the engine a few times.Maybe your
alternator requires checking but the solution in my case was to purchase
a CTECK intelligent battery charger which I leave hooked up all the time
the car is in the garage.With all the various items sitting across the battery in
the off position, sometimes unless trips are longer with lights off (daytime)
the battery may never reach full charge.

Regards John Thttp://www.ctek.com/EN-US/DealerLocator.aspx

Chester UK

PS Charger Model No CTEK XS 3600