When you suddenly wake up, when your muscles and nerves are not awake, you will be clear-headed and unable to move. This is called a nightmare. That is, it is often accompanied by a sense of oppression and chest tightness, which wakes the sleeper. I had a dream when I was sleeping that I felt depressed and had difficulty breathing, which was mostly caused by excessive fatigue, indigestion or excessive tension in the cerebral cortex.