This might be the million dollar question.
Speaking as universally as possible, the 2nd and 3rd years of college are the least motivating, for sure. It's no longer new, but graduation seems so far off. People start changing majors. You learn where the parties are and who to attend them with. The whole experience starts to become a significant investment in time and money.
I guess the big question is this; why are you being lazy in your studies? Are you lazy in other aspects of life? If not, I'd probably assess why you're in college. Are you there because your friends went so you did too? Is it family pressure? Do you truly love your major? Were you told that college is the way to go if you want to be successful in life?
If you truly love your major and you're content with it but can't find the motivation to dig into the books and study, that's one thing. If that's the case then you should try to form or join study groups with students in your courses, spend more time in the library and at campus study spots, join a professional society that supports your major (most offer significant student discounts), attend professional conferences related to your major, and start networking with established professionals now. Also, don't be afraid to do more than one internship. Employers eat that up.
If you're in college for any reason other truly loving your major you should get out now. Higher education is pushed entirely too hard in this country. Trades and skilled jobs are where the bread and butter are. Your professors will never admit it, but, college is nothing more than a financial engine that exists to create an excess of wasteful and irrelevant administrative positions, a massive loan and banking industry, and an entire universe of sports, sports media, sports merchandise, etc. Look at the people in your life who have gone to college and those who haven't. Ask yourself if one is any better off in life than the other.
I'm not encouraging you to quit school. I'm simply telling you that college isn't for everyone and it's improperly marketed in this country. There's also nothing wrong with taking time off, working, and making up your mind later.
Best of luck!