Where do they come from..

Recently at night I have been getting considerably strong energy surges from below my navel up to my solar plexus (where it stops).
Once it starts each cycle lasts about 3 seconds and continues indefinitely until I move my physical body. There are no strange sensations there the rest of the time.

I have spoke to someone else who experiences similar stuff and they have related it to AP, though I was wondering if it means anything in particular?
It is quite different from other sensations and has just started out of the blue
Possible a blockage in the heart center?.. or over activity?

Peace