Enjoy the calm before the storm. This is either your last or 2nd to last summer off of the rest of your life, depending on if you do research over MS1 summer.
There are a multitude of threads on SDN highlighting the pros and cons of "pre-studying" before MS1. Maybe peruse those and decide if you think it's something you want to do. I did nothing pertaining to med school in the summer before I started, and I wasn't worse off for it and I don't regret enjoying that summer. There are some people who believe they benefited from "pre-studying," so YMMV.