I woke up during the night, around 1:30am, with a dry mouth, needing to go to the toilet. It felt like my heart was racing, not too bad and I wasn t breathing fast. I then got this warm feeling in my upper body, but at same time felt cold and started shaking from feeling cold. It s happened before but not for a long time now. I usually have to sit up until it passes. Is it something to be concerned about? Why do I just wake up from a deep sleep feeling strange?