I didn’t start reading comics until I was in college and it was movies that pushed me to pick up my first graphic novel. I was also really nervous about where to start and going blindly into comic book shops. I would recommend doing research on your favorite characters online and just talking to other fans. Most of us can point you in the right direction and are more than happy and excited to do so.
Also, please don’t let this nervousness stop you from picking up your first comic book. There are entire worlds for you to discover. And it’s going to be awesome.