My iPhone 16 does not turn on

FIRST: To turn it back on, hold the SIDE button for a long time (up to 30 seconds). If that doesn’t work force restart it:

• Press and quickly release VOLUME UP

     then

• Press and quickly release VOLUME DOWN

     then

• Hold the SIDE button until an Apple logo appears (15-30 seconds), ignoring "slide to power off" if it appears

The operative word here is QUICKLY for the first two buttons; and try it a couple of times, the timing is a little tricky. If done correctly this will always work unless the phone has a hardware problem.