T.S.
I am a first time mom also so I don't know if this helps. My one year old daughter starting do this last month. I would not have thought of this myself but a freind suggested this might be the problem. Something about needing more calories because of the increased activity. So i started giving her more to eat during the day. It only took two days of extra snacks and she's back to sleeping sound all night long.
P.s. It's not bad mine won't even let me hold her anymore to much to do LOL. Soak it up if you can:)