Wait for strong neck control around 12 months before riding. Your baby must sit...

https://www.bookmarkidea.win/wait-until-your-baby-sits-unassisted-and-holds-their-head-steady-typically-by

Wait for strong neck control around 12 months before riding. Your baby must sit unsupported while wearing a helmet. Use a trailer for infants. Once they hit one, front seats offer interaction and rear seats add stability. Talk to your pediatrician