Hello randomUser124,
There's two ways to go about this. The best way is to use a connection profile that doesn't require username and password. The worst way is putting the username/password in a plain-text file and referencing that with the auth-user-pass directive. Both methods will lead to a solution that doesn't require the user to interactively enter the credentials, so that the connection can be established automatically.
If you're using OpenVPN Cloud or OpenVPN Access Server you can arrange things so that it doesn't require username/password.
Then you can run OpenVPN Connect v3 as windows service daemon:
https://openvpn.net/vpn-server-resources/use-openvpn-connect-v3-on-windows-in-service-daemon-mode/
Good luck,
Johan