Try wrapping him in a blanket securely and rocking him or singing to him or just holding him. If that helps, it could be normal. Maybe he is teething. Some babies just cry a lot and nobody can tell why, and it is hard to deal with but they do grow out of it. As they grow, they might want to stay awake and play for longer, and they can go a bit longer between meals. But if you have tried everything that you can do and you are still concerned, call your pediatrician.