Is there a default style.css

You can certainly use it, but it is not going to cover everything. Plus a lot of the style is going to depend on how you structure your content and other such items like your menus.

If you are looking for just a blank stylesheet that contains all the default classes and such that WordPress uses in outputting the content, there is an article on CCS Tricks that has a pretty comprehensive list.

One thing I would advise is learning SASS to help you write your CSS faster and also develop a workflow that can be ported from site to site. It also has some nice time savers like calculations and variables (e.g. $baseColor: #0000ff; background-color: $baseColor)