I noticed the middle of my abdomen sometimes showing the movements of my bowel after my last big surgery in 2017, where I had a total obstruction. It looked strange and a bit scary, and I wondered why I hadn't seen it before.
In fact it is a hernia, the abdominal wall has not closed completely after the incision of that 2nd big surgery. I didn't do anything about it because by GI doc said it is big enough so nothing will get stuck there. Treating it would mean another surgery with insertion of a flexible mesh to hold things together.
I have no problems or pain with that hernia, it only looks a little weird occasionally.
Perhaps such a hernia is what you experienced.