should i be worried

It is kinda recommended to sleep on sides only(specifically left, but of course on the right can too) and avoid the back position especially after bump is getting heavier that can effect blood flow/oxygen delivery to ur baby area; I also experienced those kicks especially in the morning when two of my sides sore to lay on and I m doing kinda half back position with soft pillow under my back yet it only last for a minute till baby is giving a sign (I just assume so) that not comfy for her… But it really depends, my friend was peacefully sleeping on her back through the second trimester with no problem, her baby is 2 yo; Triple check with your doc and don’t worry

Don't worry, what you felt is likely just hiccups or a strong kick that felt rhythmic because of the position you were in. At 22 weeks, baby movements are still quite subtle and change based on how you're positioned, so switching to your side probably just shifted things around and made the sensation stop. That said, if you start noticing any patterns where movements feel off or if you're ever unsure, it's always good to mention it to your gynae at your next visit just for peace of mind.