Most experts recommend waiting until your baby reaches the 9 to 12-month mark...

https://sierra-wiki.win/index.php/Is_Riding_on_the_Sidewalk_Actually_Safer_for_You_and_Your_Child%3F

Most experts recommend waiting until your baby reaches the 9 to 12-month mark before riding. Your little one needs rock-solid neck and core strength to hold their head up comfortably while wearing a helmet