I always tell my husband that our little girl will probably end up playing as much football as he did, because sometimes she just won't stop in there. I'm quite suprised. I mean even today (37wk 3 days) she was going psycho. Some babies are just more active then others, it may also depend on us. If we're a bit stressed or not so chilled out, I think that also effects our babies, that's what my midwife told me and I also believe.
Just think of it this way, it's much better to have a baby that's active in there than feeling almost no movement, it keeps our mind at ease that everything is ok :-)
My little guy will do that sometimes too, so it's pretty normal. Sometimes it's something you ate/drank, but sometimes they are just in a position where they can move a little better. It's hard to believe how much they move around in there with such little space, but they find a way.