That sounds like my daughter! Aurelia has been doing three or four naps of exactly forty minutes each since she was ten weeks old. Recently we've begun swinging her in her hammock after about thirty minutes (when she comes into shallow sleep), and if we persist through this restless phase she makes it through to 1hr 40m. We have been trying to encourage this longer sleep at the middle of the day as she finds it so difficult to stay up in the early evenings, although she wants to. It's working well so far - hopefully she will get to the stage where she just knows to nap for that long. So, I can recommend any kind of movement. Good luck!