Sammeh,
Don't worry about it. It's called sleep paralysis and it happens to perfectly normal people. It can happen when we're especially tired or stressed. It also happens more often during afternoon naps although it can happen any time we try to go to sleep. When we sleep, our body is paralyzed. That's to protect us from acting out our dreams. Sometimes the body goes to sleep before the brain does. You may hear a buzzing or electrical sound in your head. You might feel pressure like someone is sitting on you and it's hard to breath. You might also hear people talking or moving (a common one is the feeling that someone sat down on your bed). Sometimes, when it happens to me, it feels like I'm levatating off the bed. LOL Darn! If only.........
I know it can be really frightening, but you won't stop breathing and you won't die. You'll either struggle to wake up and succeed, or your brain will catch up to your body and you'll finally fall to sleep. Get some rest.