It may be related to the learning atmosphere in the university. Compared with high school, it's much easier and I'm not used to it at once. I don't know what your major is. If it is science, find some exercises and questions to think about. The process of thinking can help you concentrate and learn deeply. If you are a liberal arts major, you might as well read more books, but the course study should not take too long, because the theoretical knowledge of university study is far from the needs of the market and society. Reading more books and reading good books can cultivate one's temperament and improve one's quality.

If you don't want to think or read, go out for a run and take a hot bath. It is very important to combine work and rest and re-develop good study habits. I hope I can help you!