What Causes Sensation Of Warm Liquid Passing Under Skin Of Abdomen?

Over the past several years I have had the sensation of a warm liquid passing under the skin, upper right abdomen. Does not happen every day, or even every week. Doesn't hurt at all, just feels like warm liquid moving. Asked my family doctor and she had no idea what to think and had no suggestions as to finding out what it was. It went away for 3-4 years, and recently has started up again. I've had no change in my health or lifestyle that would precipitate it starting again. Any ideas??