Don't Install iOS 11.3 If You're Unprepared
If you haven't prepared yourself, or your device, for the iOS 11.3 update, do yourself a favor and wait until you've properly prepared.
It's impossible to predict how your device will handle the transition from iOS 10 to iOS 11.3 or iOS 11.0/iOS 11.0.1/iOS 11.0.2/iOS 11.0.3/iOS 11.1/iOS 11.1.1/iOS 11.1.2/iOS 11.2/iOS 11.2.1/iOS 11.2.2/iOS 11.2.5/iOS 11.2.6 to iOS 11.3 and that's why we recommend doing some prep work before you install the software on your phone.
We've put together a guide that will walk you through our pre-installation process. Some of the steps will take you a few seconds others, like backing up your phone or tablet, might take you longer.
A little preparation will go a long way toward preventing problems so make sure you take the time to properly prepare your device for iOS 11.3.