Do you have a Sony Xperia Z1, and the screen appears to be dead / off, but the phone is actually on in the background (to verify if it is on, try calling it from another phone for example).

The following trick will probably fix the problem:

  1. Hold down the Volume Up button and the Power button for about 10 seconds.
    You should feel 3 vibrations. This will turn your phone off.
  2. Wait a couple of seconds, 20 or so.
  3. Hold down the Power button for about 3 seconds.
    This should turn the phone on again, and this time the screen should come on too!

Please note that there may be several other problems resulting in a black/dead. This trick is not guaranteed to solve all of them.

Please comment below if this trick worked for you

Update Apr 16:

I have reached out to Sony Mobile regarding this problem.
They said the dead screen is probably caused by some apps that make the system hang. Although I think there is something wrong with the system, since other mobile devices don’t have this problem.