Power Button/Screen Lock: Pressing it Restarts Phone

"What you describe is very similar to the symptoms of a bad power button, but there are some things that aren't typical. For instance, when a power button is bad, it's usually hard to get it into recovery mode, and it may restart or shut itself down once it's there. Power buttons that are working intermittently or partially stuck can have some weird symptoms though, so there's still a possibility that's what's wrong.

If it is a bad power button, it will probably need to be replaced. Not sure what kind of power button that phone takes... many Samsung buttons are soldered on, but some are on a flex cable and can be replaced without soldering. The only thing I've found that helps a power button (other than replacement) is that sometimes putting some electrical contact cleaner on it (if it's the soldered on kind) and pressing the button a bunch will help. If you don't have any electrical contact cleaner, you can try some isopropyl alcohol with a bit of wd-40 in it. It's a long shot, but it worked for me a couple times before I learned to solder them!"

Facing exact same problem with my galaxy tab 4 7.0 . Please give me some solution.

"same problem, how I get my HTC sensation 4G broken power button to power on with out a system. step 1: remove the battery from the phone. step 2: plug the phone without battery to a socket using a good cable. step 3: put back the battery when the phone is still connected to power, press and hold the up volume key and just tap on the volume down key while pressing the volume up, when it has on immediately Download volume button as power button

APK

Version: 1.1.1 change your power button to the volume button welcome back start using your phone back"

i have allraddy do this

"cheng on off switch.

Update (12/21/2017)

just change on off switch"