I read a lot about "repetitive behaviours" amongst autistics and whilst I have several stims, I'm not sure whether they're classified as "repetitive behaviours".
I grind my nails together until they're smooth, and I have a dent in each thumbnail because of this. I remember having the same dent because of this habit back when I was a kid. One weird thing my parents told me I did as a baby was to search in the carpet to find a hair and then I'd lay it across my dummy/pacifier and then put it in my mouth, which is gross but I seemed to enjoy it as a kid, I think it was the texture/feeling of the hair lol.
My grandmother looked after me the most as a child, and she's dead now so a lot of my behaviours as a baby are a mystery now.