baby crying from sleep and in consolable

My baby is 4 months old. Has been crying from his sleep at night after putting him to sleep.( usually yhis happen within 30mins after he fall asleep) He can wake up crying And the crying is the inconsolable type. And eill take some time for us to csrry snf rock him before he calm down Anyone know the reason? Is this like what old folks ususlly say baby got frightened? Or due to sleep regression or overtired? What should i do to prevent this