I have a spasming or twitching around the bottom right of my belly button that lasts for several minutes. It's not uncomfortable, just annoying.

Try stretches. When you have a spasm, you might try an abdominal wall stretch by lying on the floor or bed and lifting up the upper body by extending your arms and arching your back. If there is any abdominal pain or nausea or sharp cramps, get checked out for an umbilical hernia.