What's his day look like? Are his naps starting to get shorter - 1hr15, 1hr20ish? If so, he may just be getting OT and need a bit more A time in the day to make his naps long enough to be restorative again.
He may be hungry - if AF has come back, your supply may have dropped a bit and the evening feed may not be as much as it was a week ago, yk?
Any other changes in the household? Gone back to work, different sleeping arrangements, stress? LO's can pick up on that...