Nox - a similar thing happened with my DD at 6mths! Apparently when they start becoming more active (rolling/crawling etc) they "practice" in their sleep and can wake themselves up, also they replay their activities in their minds alot so they may be more restless.
What I did - I stopped feeding her in the middle of the night - I would only feed if it had been 6-8hrs after last feed (overnight only, was feeding more in the day!) that helped us, and she gradually got into a new routine and she went back to being a good sleeper.
Do whatever works for you, but I think its a stage
HTH! All the best