It's never too early and it's never too late. Most students start their internships between sophomore year to junior year. But experience is experience and the more of it you get the more you will learn and increase your chances in landing a job of your liking. Don't be afraid to apply for an internship for the summer after your freshman year, for that I would suggest applying around January time-frame and keep applying. You also have the option to volunteer during that time or help conduct research for a professor in a field of your liking.