Oh FFS girls, due to the laws of physics ghosts cannot physically exist, and due to the fact sound is the movement of air, the fact that they can't physically appear means they can't make a noise........
Any feeling of cold or someone being sat on your chest is your bodys heart slowing down during your sleep pattern, often making you feel paralysed.
Sometimes when your heart slows too much your body will "jump" you awake, it happens to all of us. Basically it's an over active mind.