it's never too early to start reaching out and networking, and mentors will understand if you express interest but suggest that you hold off for now as you get settled into medical school
even if all you do is read some of the literature coming out of labs you're interested in, and becoming familiar with what they do (this may even dovetail nicely with your studies), this will not be time-consuming but could have some value
this is piggy-backing on the poster above who said that you might put your toes in the water before MS1 summer without a big time commitment
what is an excellent idea, which goes along with reaching out to different depts, is to consider supplementing what if any clinical exposure you get already from your school, with some on the side specialty shadowing
even an isolated day shadowing in clinic here and there in fields you don't get to experience from MS3, can be illuminating and is not time intensive
showing that sort of interest, if you do continue on with that dept, can sow the seeds of networking and getting hooked up with good projects, with little initial time investment
one of the biggest mistakes/drawbacks of medical education is not getting enough exposure for good specialty choice
so if you can get in with PMR early, etc, that can work you towards end goals without taking away from your studies