Create a calming routine before bed. Switch off TV or any screens at least 15-30min before sleeping. You can read some books to prep for sleep. If u are into essential oils, u can read up more about the types of oils that you can diffuse to create a calming environment. If all else fails, be with your child when he wakes up crying and soothe him, knowing that mum's around to chase away the scary nightmares.
how long has it been? some point of stage, they went through this. if it has been long. it may have to do with over stimulation before sleep
Happened to my son for the past 1 year. Then he was OK for a while and then back these few days. He will wake up and crying and kicking.
How old is your Son? Do you let him watch tv/Youtube before bedtime?
Are u playing with him too much before he sleeps?
How long have this been?