Any change in routine? Did your little one recently come back from a holiday? Try having him co sleep with you for a little while. My lo was like that when we moved him to a new bed.He was totally happy in the day, but obviously internally he must have felt unsettled and that came through in unsettled sleep at night.
Sounds like sleep regression. Toddlers have funny patterns, hard for us to understand. Sometimes I would go with the flow instead of burning my brain cells to figure out what's wrong.
Anonymous