My niece is like that. It's like she never stops moving and stretching. She's done that since she was born (and probably before that, lol) and she is now 4 months old and, for lack of a better word, perfect.
What babies are doing when they "stretch" is called "pandiculation." It's what cats and dogs and all vertebrate animals do when they get up from rest. It readies the muscles for action. Adults do it as well when we wake up and yawn and "stretch out" before getting out of bed. It's very normal, very healthy, and "wakes up" the muscles at the brain level so that the baby can begin to learn to move and integrate sensory motor patterning. All humans learn through movement, and babies are amazing to watch as they figure the world out this way.
Why does my Baby stretches both arms most of the times.
I have a baby girl.. she is 5 months now , and she almost always keeps her both arms stretched wide open, again she is very normal sometimes with both hands to normal positions.I think that is not "pandiculation", but why she does it I can't understand... Please, say if it is normal.