Moto G5 Plus comes with the latest version of Android, which is 7.0 aka Nougat. On the internet it is said that Android 7.1.2 arrives for Pixel and Nexus devices, may be google will soon roll out this update for G5 Plus too. To find the android version of your phone, go to Settings and scroll down to get the About Phone option where it shows the version of your phone. Tap on this option and on the next screen tap on Android version 7.0 three times to see the logo of Nougat.
On the same screen, at the top you could see System update option. Tap on that when you are connected to the internet and for now it will show the message – Your device’s software is up to date as there is no update available for the G5 plus.
Usually your phone will intimate when a new version is available, you could also follow the above steps to check it manually. When a latest version is available follow the on screen instructions to get your phone updated with the new version and then your phone will restart automatically.