Crying loudly could be over stimulate. Dont let him play too much and watch too much tv few hours before bedtime. and if he wakes up w.o crying, only want attention, just let him be. dont give in by turning on the tv or play with him. Last time my son often wake up at night too, but just for attention. We told him to go back to sleep and ignore him. and usually he will sleep back within 5 min. After sometime, he stop waking up every night.