DD is 11 weeks, sleeps pretty well at night from dream feed onwards, settles quickly and doesn't stir from one sleep cycle to the next (I think they're about 45 mins?).
Naps in the day are another matter - she'll sleep well for 45 mins, but will wake herself panting, kicking her legs, squeaking, snorting etc etc... It often takes half an hour or more to help her settle again, at which point she goes into a proper deep sleep. She's swaddled pretty comprehensively, has a dummy (which she spits out a lot when restless) and I help her back to sleep by putting my hand on her chest, shushing and stroking her temple / nose which makes her eyelids droop!
She does the same when she goes to bed in the evening - drifts off for 20 mins or so then wakes up and fusses / grizzlies for at least an hour, then goes to sleep & is dead to the world.
Any thought on how to avoid these super wakeful, restless patches between sleep cycles - will they get better on their own?