Why do iPhones sometimes just go blank and black screen?

My iPhone goes black sometimes and then I have to push the side button for it to turn on again. I have to hold it down and it works. But why does it happen?

It's the screen timeout function. Just go to screen settings and change the screen timeout function. You may also have to change the lockscreen timeout function to match it. It just depends if you have that set up or not.

Wat?

Your screen is almost out of work, you should buy a new screen to replace it.
So you can buy the replace screen from the amazon, hcqs.cc