Quick Answer: To restart your iPhone without the power button, go to Settings > General > Shut Down, then slide to power off. You can also ask Siri to restart your iPhone without the button.

The physical home button is no more, but there's a workaround you can use on pretty much any iPhone.

To restart your iPhone without the power button, you can shut down via settings, ask Siri for help, or let your battery die. Then, recharge or turn back on.