What would cause a "vibrating" sensation around the umbilicus?

Muscke twitching: It sounds like a muscle twitching. Muscle twitching is caused by minor muscle contractions in the area, or uncontrollable twitching of a muscle group that is served by a single motor nerve fiber. Mostly, it is temporary stuff but if it gets worse and getting more often, you have to see your pcp for a possible neuro-muscular disease.

Vibrating sensation: The intermittent tingling in lower abdomen needs to be looked for the following causes; 1) the area is supplied by the dorsal or thoracic spine (middle portion of the back). Any pinched nerve because of the bone spur or degenerative disc disease can be responsible for this. 2) deficiency of vitamin b 12 is another cause which can produce the symptoms.3) if the diabetic profile like glycosyl.