If you're in need but think you don't have the tools, restarting your iPhone without the power button simply requires ... Normally, you would then turn the device back on with the power button.

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.

AssistiveTouch is an accessibility feature on iPhones and iPads, offering a floating menu that helps users to navigate with ease—no physical buttons required.