I think its probably developmental - to do with increased mobility and if its that, you just have to ride it out. If he's happy, leave him. If he's getting upset, use shush/pat and see if he'll go back to sleep. If he wakes within an hour from that, give him a small feed in case he's hungry.
The baby rice... pretty tough on little tummies - did the wakings start shortly after starting the baby rice? If so, when are you feeding it to him? Best to do solids in the morning an hour or so after milk when you start out so it doesn't affect the night so much.