I have mentioned before that we had a very fidgety baby. It's been a while sinced I talked about it. Although she is still pretty fidgety, at her currently toddler stage it seems more normal and has in many ways translated into bigger, general movements, like climbing.
But I still get a ton of search hits that have to do with baby fidgeting or flailing while sleeping or nursing. Some people stay around and read a bit, and I hope they get what they need from the posts I wrote specifically about this topic hoping that others realize they are not alone. Most people don't stay at all, and I figure they are probably looking for medical reasons why babies fidget (like I would).
Then I got this comment, which does indeed show that people are looking for medical reason. Anonymous said that she wasn't sure if the Pumpkin's fidgets were as severe are her 3.5 month old. Well anonymous, I can't be positive since I haven't seen your child, but at some points they were as bad as you describe. There was a range from little fidgets to oh-my-goodness-what-is-wrong-with-my-baby fidgets. Some were very violent both while sleeping and while nursing, and Londo and I were so worried at times that we would call up the doctor and talk to her about it.
I also searched online and in books for medical reasons why a baby might fidget and talked those reasons over with the doctor.
I found that when a baby has trouble settling to sleep and arches her/his back violently while nursing, these can be signs of GERD, or severe acid reflux. This is usually accompanied by other symptoms, and if someone suspects this I suggest they not only look up GERD online but talk to their doctor about the likelihood that this is the issue. I also suggest you think about silent reflux, as that might be the cause. Our doctor did not believe that the Pumpkin had this issue, since none of the other symptoms were there.
The other major cause of this fidgety/squirmy/flailing in babies (especially when asleep) is gas. Some babies are just more gassy than others. Even if you don't hear all that gas come out, the gas bubbles could be working their way through the baby's system. As my doctor said, babies are not born with their systems fully formed. Right around 3-4 months is when the digestive system is really working out the worst of the kinks. Our doctor believed that this is what was happening with the Pumpkin.
The treatment? Time.
Isn't that the worst answer? And yet, I can attest that over the last 16 months of the Pumpkin's life, it has really gotten a lot better. She does go through gassy periods, and she goes through sleep regressions, but she's healthy and happy. Since she's been able to move more and more on her own, she's (and we've) able to deal with her fidgeting better.
Another "medical" condition that we think might affect the Pumpkin's fidgetiness (I made that up! Like it?) is teething. Our little one seems to fidget A LOT as her teeth are moving their way through the gums. I imagine she is in discomfort and trying to either find a comfortable place to be or distract herself. Her teething is always worse at night, and she did get her first tooth around 4 months.
And my last reason for why babies fidget...
Some babies just fidget. I'm sorry if that's not the answer you are looking for, but it's the truth. Just like some people are fidgeters (my husband is an example) and others are not (I'm not). Babies are just little people. But they can't control their bodies as well, so this is likely why their fidgeting takes on the epic, flailing proportions that it does.
The swaddled helped us. The swing helped us. Constant moving on our parts helped assauge her need to move and fidget until she could do more on her own. This meant lots of walking and rocking and jiggling and whatever else would work. It was NOT easy to go through, but there is not much you can do about it. I kept hoping that the doctor would say "Oh, sure! Your baby has X, and you can treat it with Y and everything will be fine." No such luck.
I do believe that this aspect of my daughter's personality translated into her early gross motor skills and possibly her fine motor skills. Her need to move constantly propelled her into early crawling and early walking and now her constant climbing. This is a really neat aspect of her, one that has been fun to watch develop.
But she does still fidget. I wouldn't dream of cutting my hair at this point, because she uses my hair as her main fidget while nursing or trying to fall alseep. I can put up with that, if it helps her calm down. I've tried to switch her to a toy or blanket--it's not the same. But that's okay, because it's not nearly as bad as it used to be. She still has trouble getting comfy, which includes fidgeting, flailing and even violently pushing and kicking. We are nowhere close to being able to put her down "drowsy but awake." But I've been assured that she will eventually be able to go to sleep on her own. Like when she goes to college. I hope.