Anyone else have a baby that likes to lift their legs and slam them down over and over again. Both…

Anyone else have a baby that likes to lift their legs and slam them down over and over again. Both my twins have been doing this since they were about 3 months old. But my girl twin does it way more now. My boy twin pretty much does not do it anymore. She does it in the middle of the night and I jump straight out of bed. She was just doing it now like crazy, after she woke and I put her back down. I googled it and it says it could be a way of self soothing. Yeah a painful loud way. You can hear her hitting her ankles on the end of the rock n play but it does not bother he, only me