ok, so it sounds like you know what to do, Max is the same way when he's tired, just like a baby right?
He will be 5 months on 04/07 and he goes thru stages, he'll be fine one minute and the next he just keeps biting me, I try the firm NO, replacing my fingers with toys, everything and he doesn't calm down until I put him in his crate! he doesn't fuss or bark... he just walk right in and lay down...Is this your first puppy?