He probably wants food or attention. Cats are most active in their hunting at dawn and dusk in the wild.
This is a common "problem" for cat owners. The best advice I can give is to completely
ignore him if you want the behavior to stop. It will take a while, but it does work. A good 15-20 minute vigorous play session right before you go to bed at night can also help.
Any other response is only going to reinforce the behavior. Some people get up and feed the cat, then go back to bed. Their cats have them well trained!
There are a ton of threads about this; you might want to use the search feature to find more info.