Many of us at Peripheral Neuropathy have had this buzzing/vibrating thing at one time or another.

This may be due to an entrapped nerve that is getting stimulated now and then. There may be scar tissue that is entrapping some nerve. Most sensations in the abdomen are referred thru sensory nerves. So they may be odd and atypical.

Those fasiculations however, should be looked at.
Low magnesium can be a cause. Just about 70% of people in the US do have subnormal magnesium levels.

Here is my magnesium thread:
http://neurotalk.psychcentral.com/showthread.php?t=1138
This is a pretty big subject. And now there are a couple of books on the subject. Dr. J. Cohen is mentioned at the end of that thread.

Also twitching may occur when blood sugar is low. This is often the first sign of insulin resistance, and may progress to type II diabetes, if not controlled by diet. Up to 70% of people who have low blood sugar spells, report muscle twitching or cramping.