How to fix an iPhone SE that freezes during boot up and gets stuck on black screen?

Because your iPhone SE has been stuck, a standard reboot or soft reset is unlikely to help. In this instance, you can do a force restart as an alternate reboot. This approach will force your device to reboot, as the name says. There's no need to be concerned about losing important data because none of your personal information saved on the iPhone will be affected. All it does is fix any software issues that may have stopped the iPhone from performing its normal bootup procedure and caused it to become stuck.

• Press and hold the Power and Home buttons for at least 10 seconds to forcibly restart your iPhone SE. When the Apple logo appears on the screen, release both buttons.

You may need to press the buttons for a little longer since the device may not be able to load the operating system at a regular speed because some segments may have crashed. A forced reboot, on the other hand, may be able to fix whatever is causing the iPhone system to malfunction.