headlights got left on all day ,drain the battery, replace battery, now the car has a real hard time trying to start in the morning. but once it starts , it starts like normal the rest of the day, what would cause something to quit working in the starting of the car by replacing of a battery?

i want to thank this forum and the people who on on it foir the techical support that it supply us,it was the silver box with the 10amp fuse in the top hidden behind the battery, of which i whould have not even look there.. the car run great again.. thank you very much.. 1987 190e 220,000 miles on here. and she still going... thanks