Well you've heard the expressions "sleeping like a baby" and "slept like a log"? Humans go through the same things sleeping like cats. This is normal for yong cats.

As one sleeps on a surface blood flow is restricted to the parts of the body right near the surface. One rolls over to allow circulation to resume.

Growing kittens (and human babies) turn over or re-adjust positions more often proably due to their higher blood flow rates.

Sequential still photos (time lapse) of sleeping people show this too. If you sleep on a waterbed or one of the new foams, then not so much. You turn over many times in a night.

Slept like a log, not good. Wake up with a bad back. Sleeping like a baby is very good.

Wait til you fuzzball turns about 2. Then the "sleep like the dead" happens. Limp like a rag, tounge hanging out, won't wake to loud noises. Must be shaken to be stirred. (Yes, its a James Bond joke) It's freaky, but normal too. At least for cats.

Enjoy them at all ages.