What does it mean when i lay down and feel my stomach knot up for a minute and then go away?

Stomach knots: To answer this question it is important to distinguish whether the "knot" is in the stomach muscles (do a leg lift lying down to see if it makes it worse) or inside the abdomen, in which case it is mostly likely a cramp in the colon, which may be caused by gas, food, or constipation.

Abdominal pain.: Most likely you are experiencing a colic or intestinal cramp. Consider to be examined to rule out serious conditions.