My 11 month old son constantly throws his head around, it's like he's got a wobbly head..should I be worried?

My little one is 11 months old in a few days and for the last month or so he seems to be throwing his head around alot. He always shaking his head quite vigerously!!! At first we thought it was just a little cute thing that he did occasionally but now he seems to be doing it all the time and it's concerning me. He seems to be developing normal. His motor skills are fab. Verbally he's only just saying "muma". I don't know if I'm being paranoid or not but I'm just a paranoid mum because I love my boy so much. And help or advice would be fab xx