Do you lay around in bed and watch TV before going to sleep? Things like that can fool your body into thinking that the bed isn't for sleep and can make it difficult to get to sleep.
are you serious or joshin' w/ me???
Nope... it's the truth. It happens to me all the time in motels. If I watch TV while I'm in bed, I can't fall asleep, but if I turn off the TV before getting into bed, my body relaxes a lot better.
Another thing that may contribute is if you use the computer or watch TV immediately before hopping into bed. These activities can overstimulate the brain and not allow you to relax right away. It's always good to do something calming or low-stimulus before going to bed.
As an aside, a male's body produces a sleepy chemical during sex, so doing that right before you roll over and go to sleep works well too.