Sometimes, if we miss the baby's window where they are sleepy, by the time they go down, they're overtired and it takes them longer. Is he getting enough naps during the day? Not enough sleep during the day could make him overtired by the time his bedtime rolls around.

I don't think its a tantrum. They really don't have them at this age. Does he like to be rocked before bed? What is the ritual you have before bed?

There's a great book called "The Baby Whisperer" by Tracy Hoag, I think is her last name, it really helped me a lot reading the signs of my daughter being ready to sleep, being overtired, etc. It's in paperback and really has a lot of good info.