Machines using build 1803 will be upgraded to avoid risk when it reaches end-of-service in November
Small businesses and home users with Windows 10 installations older than a year will be automatically upgraded to the May 2019 Update to avoid systems falling out of support in November.
Despite widespread concerns over the way Microsoft implements its biannual operating system (OS) upgrades, Home and Pro users will be automatically kicked into using version Windows 10 1903, issued just a couple of months ago.
Source & more info: ITPro