[META] Not a moderator, but please respect the subbreddit rules and not comment stuff that is quite frankly stupid like "Dunno." This is an academic environment, not some place for shenanigans.
OP, I would recommend you look at a sociology or anthropology forum.
No, it was not common. It was extremely uncommon but not unheard of. He was not the first person with the name.
Amongst his contemporaries, there was Muhammad ibn Maslamah who was from the city of Madinah. The Encyclopedia of Islam lists several sources which collected the names of people named Muhammad before him. The feminine form, Muhammada has also been recorded. You can find this under "Muhammad" in the Encyclopedia of Islam.
fyi, a little tangential info on the name which might be of interest
a bit related to the question: did arabs call friday jumuaa before islam?
Related to this: did the name Jesus (or its Aramaic version) exist before Jesus?
Followup question that might be useful for answering this question: Is the name Muhammed or a closely related name found anywhere in the Arabian epigraphic corpus?