Before you contact help.apple.com/iphone for help, you should try to solve the problem by completing more steps. After performing the following steps, you will eventually find that your phone is working normally again. And, hope it can repair the support.apple.com/iphone/restore screen on your iPhone. Before reinstalling the operating system on your device, you must update your device. Sometimes, simply updating the device can solve the problem:

Use a USB cable to connect iPhone to the computer first

After the two devices are connected, you will see a message on the screen

The message will be similar to "There is a problem with the iPhone and needs to be updated or restored."

From the two given options, select the "Update" option

Doing so will install the latest iOS on your iPhone

Moreover, you do not have to face any data loss.