It is not uncommon for babies to have sleep problems or wake up repetitively at night. Even those who used to sleep well can have sleep disturbances at night.
Why it happens
Sleep disturbances in babies that happen due to night terrors usually happen due to sleep deprivation.
Other causes could be having bad dreams, anxiety, illness, or part of his development.
What should I do about it
Unlike what most mothers would do, don’t try to soothe him or wake him up when he seems to have night terrors.
All that you need to do is to stand and watch him to make sure he won’t hurt himself.
When he wakes up after a nightmare, reassure him and soothe him for a few minutes
Make sure he is getting enough sleep. Set him a constant time every day to go to bed and nap. The less he sleeps the more he is likely to wake up at night.
It may take a while to get back his regular sleep habit, but the more you stick to the routine the sooner the problem will be solved.