"My son is almost 6 months old and is growing fine. I've heard from almost everyone that sleep begets sleep but not so in my son's case. On the whole, he gets the sleep he needs in a 24 hr period (15+ hours) except that the sleep is never consolidated. He naps from 9 or 9:30am for about an hour and a half and then again at 1 or 1:30 pm for about an hour and a half. And usually a short 45 min nap at 4pm. He goes to sleep for the night anywhere between 6 and 8pm but rarely sleeps for more than 4 hours at a stretch before needing to wake up to feed.(he used to do 6 but now its never more than 4) It's usually either the first stretch (7 to 11pm) or the second stretch (1:30am to 5am). In between (11pm to 1:30am) he sometimes wakes up and doesn't go back to sleep (after nursing) when he's restless. He's not hungry, he's not interacting with either me or my husband (we cosleep), he just looks at the ceiling and sucks his fingers while bicycling his legs and making noises. We try to rock him to sleep and he does eventually go to sleep (but only after a long time). Spending over an hour in the wee night hours rocking him back to sleep is killing us. Any tips on preventing the wake ups? How important is it for baby to be sleeping continuously? Since baby is overall getting the sleep he needs (he makes up for his night wakings with longer naps in the daytime) should I just cross my fingers and hope that he will learn to sleep longer stretches eventually?"
I do think this sounds within the range of normal for that age. Of course, normal kind of sucks. But it doesn't sound unusual or unhealthy.
I have a few suggestions, but they're mostly about how you manage yourself instead of trying to fix your son's sleep.
The first thing I'd suggest is that if he's not crying or upset, don't try to get him back to sleep. If he's bicycling his legs and you can sleep through it, just keep on sleeping unless he starts to cry. It sounds from what you've described like he's not upset, just awake. So you don't technically need to be in the loop if being awake isn't bugging him.
The other thing I'd look at is the cosleeping. It seems like people cosleep either out of philosophy or out of practicality (or some of both). If you're doing it out of philosophy, then you should keep doing it. If you're doing it out of practicality, you might want to see what happens if you try to get him to sleep somewhere else (either in the same room or in a different room) for a couple of nights. For some reason, some babies seem to go through a window in which they don't cosleep well but sleep really well in their own space. If you're not opposed to letting him sleep somewhere else, you might try it for a few nights and see what happens.
(To get a baby to sleep in a different situation, you need a really solid bedtime routine first. Once you've gotten one established, keep it exactly the same as much as possible, and vary only what you have to to change the sleep thing. So, for instance, if your cosleeping routine was bath, pajamas, book, nurse to sleep in the bed, then your trying-the-crib routine could be bath, pajamas, book, then nurse to sleep in the glider and then put down in the crib. Or bath, pajamas, book, nurse to sleep in the bed and then transfer to the crib after 40 minutes.)
It also sounds like he's trying to drop the third nap because it's so short, but isn't really ready yet. He might consolidate his night sleep once he fully drops that third nap. Which means it's just a waiting game. If you and your partner can figure out a way to split the nighttime wakings in some way that means neither of you gets the full brunt of it you'll be better able to make it through this stretch.
He might also be up at night working on moving. The bicycling of the legs sounds like he's a kid with places to go, and that he's working on the skills to take him there. There's not a single thing you can do about that, except wait for him to really start moving.
Hang in there. It gets better. Then worse. Then better. Then worse. Then better. Then you get to be the grandma and not the mom. Anyone else have anything?