For 13 weeks he's doing very well! If he's not crying, I would just leave him alone. If you have a video monitor, do not check it. He's clearly not upset because he's not crying for your assistance. As long as he's been fed, has on a clean diaper and is just lying in the crib doing his thing, let him. If he cries, definitely go to him because he's asking for your help, otherwise try to just roll with it as he works out his sleep needs.