According to Apple, a "very small percentage" of the iPhone 8 devices it has shipped out in the past year suffer from faulty logic boards as a result of a manufacturing defect, causing a variety of issues, such as freezing, unexpected restarts or the phone not switching on.
Apple claims that these affected devices were sold in Australia, China, Hong Kong, India, Japan, Macau, New Zealand and the U.S. between September 2017 and March 2018.
Acknowledging the problem, the Cupertino giant is providing iPhone buyers with an easy means of checking if their device is affected and, if so, it will repair the device for free. In order to check if you are eligible for the free repair, you can simply go here and type in the serial number of your phone, easily found through the About page in the Setting app.
If you"re among those affected, Apple offers the option of either going to an Apple Authorized Service Provider or an Apple Store to hand in your phone for repair. In either case, the phone will, unfortunately, need to be shipped to an Apple Repair Centre so you"ll be without a phone for a while. If neither is accessible to you, Apple can also arrange for mail-in services from your home directly.
Source: Apple via Business Insider