Windows 10 normally downloads and installs updates automatically without your input.Microsoft updates windows 10 every time,and those updates can be large like 3GB.
There are many ways to prevent windows 10 from automatically downloading updates,depending on the edition of windows 10 you have.Set your wi-fi network as metered connection,windows 10 won’t automatically download updates on that connection,but instead will prompt you.You can then choose when to download updates,or take your computer to another wi-fi network and update from that network.

For some reason,windows 10 doesn’t provide a built-in way to set a wired ethernet connection as a metered connection.

To set your wi-fi connection as metered connection,open the settings app,and go to network&internet < wi-fi.Scroll down down below the list of wi-fi networks and select"Advanced Options.enable the "set as metered connection" slider here.This will only affect the wi-fi network you are currently connected to,so windows 10 will start automatically downloading uploads when you connect to another wi-fi network.To set another wi-fi network as metered connection,you have to connect to it and change the option again.Windows 10 remembers this option for each wi-fi network you anable it for,so that it will automatically set the next time you connect.
Read here for more.



https://ugokingsblog./2017/07/09/how-prevent-windows-10-from-automatically-downloading-updates/