when my battery had been drained, and it was drained nearly every night for a while there till I found the reason, the car would give one half hearted try at starting and then get progressivly more pathetic with each successive attempt. Do you have a mulitimeter? you can check the voltage of the battery to get a sense of where you are and they don't cost more than ten bucks at a parts shop. What you are describing doesn't sound to me immediatly like a dead battery, it would get worse with every turn, i.e. slower and more pathetic like. have you ever had to jumop the car?
1985 190e 2.3