Most women who gave birth live like this. They do not just wake up 2-3-4 times, or even more often times, but they feed the child for another hour. That is, they did not just wake up and then let him fall asleep again. The brain is forced to completely leave the state of sleep, and then again quickly plunge into it. How does it affect the body? Fatigue, lack of strength, depression, breakdowns, irritability and everything like that ...
Nothing good, but nothing bad either. Monks in monasteries live like this all their lives, getting up for prayer several times a night. Probably little benefit from this, but with a certain habit, this is not a problem.
Nothing special. I went on guard in the army every other day, woke up to the post as usual. After 6 months, the habit was developed to wake up at 24, 2, 4.6 hours for a few seconds - if he realized that he was not going to change, he immediately fell asleep. There were no consequences either then or distant. Or they are invisible