Baby like to throw himself back and bang his head

Hey mummies. My baby (currently 10 months) like to throw himself back and bang the back of his head rapidly especially when on the stroller. (Ongoing since 2 mths ago) Recently i google, and i saw this can be a sign of austim. Personally i dont think he is, he interacts well with us, good eye contact & respond to his name. Although he still cant understand simple instruction, he will raise his arms up when he saw we were about to carry him up. Mummies, just when to know if any of ur babies does this too? Is this a normal behaviour? Do i need to be concern of austim ?