I get that same kind of sinking feeling(as a recent person posting) when I am trying to fall asleep. Feels like I am being "jolted" out of sleep. Difficult to tell if the sinking feeling is in the chest or stomach/abdominal area. Also, difficult to determine if it is my heart skipping a beat or that I am just not breathing for a few seconds and then gasping for a breath. It is very anxiety producing and kind of scary. Anyone know what is going on? Sorry to be vague, but it is difficult for me to describe or put into words.