These may be some of the reasons you are feeling movement in the left side of your abdomen. 

1.) Peristalsis: it's regulated movement of the bowel which pushes food downward. 

2.) Spasms: Bowels are muscular organs . A spasm is a involuntary sustained contraction. Your Dr. can prescribe you a anti-muscarinic drug to help this. 

3.) Subcutaneous emphysema: air trapped under the skin. It can feel like bubble wrap when the air shifts around. It can feel like rolling.

 I've experienced this myself. I'm not a Dr. , this is just some things that I came up with from doing my own research. Hope it will be a help for you !!