A dead battery can be caused by a faulty seat control module that does not properly shut down. Spilling liquids on the front seats can cause these modules to fail.
Car Problem Reports
Mercedes-Benz C32 AMG Dead Battery Due to Failed Seat Control Module
Mercedes-Benz C32 AMG Problem
Average Mileage: 83,806 mi (73,500 mi - 94,113 mi)
Visitor, 2002 Mercedes-Benz C32 AMG, 94,113 mi
Alarm goes off until it dies; first time car was jumped by Roadside Service and this worked for about 30 days; the battery drained a second time, but this time Roadside could not get anything more than the lights and doors to work; the steering is locked out; initial diagnosis was the ignition switch and a "dead battery", but then determined it was not the ignition switch or the "dead battery", but the passenger seat "and" the overhead console modules causing the drain. Both were replaced. This seems to be a common issue on the C Class itself for the 2001 thru 2004 modules. There is also a C320 forum on the same issue. MB USA does not think the problem extends beyond just a few vehicles.
Visitor, 2002 Mercedes-Benz C32 AMG, 73,500 mi
battery was dead. I replace the front seat module.