We all use dreams to process information, LOs are the same so when they are learning something new it can effect their dreams and sleep. He's likely dreaming of crawling so the skill can be processed in his brain but finds himself starting to actually crawl in his bed which wakes him and disturbs sleep. It's very common and nothing at all to worry about.
One thing you can do is give him as much floor time as possible in the day so he gets maximum chance to practise his skills when he is awake as this may speed up the process. Less time in the highchair, stroller, car seat etc and more time on the floor may help.
Shush/pat to resettle him is fine.