He could be having a growth spurt. Is he wanting to feed more?

If he has more smelly nappies, he could have a mild case of gastro. There's a lot of it about at the moment. As long as he is still feeding well, you could try giving him some paracetamol or ibuprofen for pain releief and see if this helps him settle.

What is his sleeping pattern like? Sometimes if a baby is a bit sleep deprived they can have periods of unsettledness like this.