While using Firefox in Selenium WebDriver 3.0, it will start a default profile automatically.
But, you can create your own profile and you can name it according to your choice.
Then you can use the below code:
Profiles profile = new Profiles();
FirefoxProfile fprofile = profile.getProfile("MyProfile");
WebDriver driver = new FirefoxDriver(fprofile);
Using this your Firefox Profile will start with a new profile always. You can change the settings according to your choice.