Why is my phone opening then closing immediately?

When I open my phone by pressing the power button, the lock screen shows up then after less than a second it closes again. I tried to test my battery if it is bloated but it is not. I tried charging it but nothing happens. How can I fix it?

from Android Forums at AndroidCentral.com - Ask a Question //forums.androidcentral.com/ask-question/758481-why-my-phone-opening-then-closing-immediately-new-post.html
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