Why do I wake up immediately after a dream more often?

Well waking up immediately after a dream is because what happens there it can cause you problems in real life like your breathing can stop and problems like this , so the brain does immediate intervention !

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From what I know about dreams, you could be waking up early for lots of reasons. If you're having a lucid dream, meaning you're aware you're dreaming, you could get too excited and wake yourself up. If you wake up during a dream where you're about to die, you wake up because you can't die in dreams apparently. If you die in a dream, your brain thinks you're actually dead and starts shutting off. Also, you remember your dreams better and for a longer time after you wake if you wake up while you're dreaming, or near the end. Hope that helps.

When you are watching a dream , You are not aware of the fact that you are watching a dream. You Feel that all those things are happening for real with you. In such case, If sometimes something bad happens to you in your dream or if you feel that you are in danger then out of the natural tendency of human you try to move out of that situation and the conscious part of your brain becomes activated which leads to your waking up.

It could possibly be the dream you are having and your body is reacting to it in shock or confusion. It's all how the brain works and reacts to things

Experiencing realistic, intense, and disturbing dreams right before you wake up is a phenomenon known as “hypnopompic hallucinations.” ... As you begin to rouse, the dream-like imagery of REM sleep intrudes into your waking state. This causes you to experience the hallucinations