Son wakes up after an hour when he goes to bed and so on every time. A…

Son wakes up after an hour when he goes to bed and so on every time. And with DSD it's only after 30 minutes, when I am next to him, he can fall asleep for half an hour without waking up, sometimes. He doesn't sleep well on his chest, rocking him. What could be the reason? He is awake for 2-2.5 hours actively but falls asleep with crying. At 9 PM bedtime, he wakes up at 8 AM in the morning, he wakes up 2-3 times in between, only by rocking he can continue sleeping. I wanted to teach self-falling asleep but he just screams when he wants to sleep, what should I do, what should