Apple is releasing minor OS updates to its install base today, starting with a bug-fix focused watchOS 2.2.2 update for the Apple Watch and continuing with iOS 9.3.3, which appears to include a bunch of bug fixes and unspecified performance improvements. The update can be applied on your device over-the-air in Settings → General → Software Update or downloaded through desktop iTunes.
iOS 9.3.3 released with bug fixes and performance improvements