I created a style called “Novel” with the spacing and font that I like. When I write a paragraph in that style and hit Enter/Return, the style switches to No Style for the next paragraph and I have manually go to Style and change it back to Novel.
As an additional note, when setting up a style you can select a “Next Style” from the dropdown menu at the bottom of the style dialog. This will tell Scrivener what style you want in the next paragraph. By default it is set to ‘none’, so each new paragraph will return to ‘no style’ , your default formatting.