I smell bad thing at night it comes and goes every 10 to 15mis and stays for 5 seconds. What could it be?

Depends. We need more details to answer this question. Are you smelling a part of your body or is it some pungent odor in the room does this only happen at night.? Where are you when it occurs? Do you have any other symptoms? It could be anything from a rotting piece of garbage to an infection or a form of epilepsy to a random skunk roaming around the house.