To format the code in Visual Studio when you want, press:
(Ctrl + K) & (Ctrl + F)
The auto formatting rules can be found and changed in:
Tools/Options --> (Left sidebar): Text Editor / CSS (or whatever other language you want to change)
For the CSS language the options are unfortunately very limited.
You can also make some changes in: .../ Text Editor / All Languages
There are several to pick from in the gallery but the one I'm using, which offers considerable level of configurability still remaining unobtrusive to the rest of the settings is Beautify by Michele Melluso. It works on both CSS and SCSS and lets you indent 3 spaces keeping the rest of the code at 2 spaces, which is nice.
You can snatch it from GitHub and adapt it yourself, should you feel like it too.
Install HookyQR.beautify extension. It will beautify your javascript, JSON, CSS, Sass, and HTML in Visual Studio Code. It is the most use extensions for this purpose