Really great question!! It's good to hear that you are thinking about internships during your time in college as they are often some of the most rewarding experiences during your time as an undergraduate student. In my experience, I have found that it is best to start interning as early as possible. College goes by surprisingly quickly and you don't want to have graduated without having had an internship or two. Sure, many internships are geared towards juniors and seniors, but there are many internships that are also geared towards freshman and sophomore year students as well. I had an internship overseas during the summer between my sophomore and junior year and that internship set me on a path that led me to where I am right now!! It expanded my interests and led me to the great job that I have now. If you are able ti find an internship during your freshman or sophomore year, go ahead and do that internship as it can only help. Having more work experience can only help and make you a stronger candidate for when you apply for a full time job after college.
I hope this helps and I wish you the best of luck in your internship hunt!!