I’ve had similar problems evoking emotions. The first step I took was spending time with people who had more apparent emotional range than I did. (My background is science, so this meant spending time and building friendships with more people on the creative side.) I also have taken some acting courses (which were very good at sense memory), including a couple of improv classes. I’ve done journal writing, most free form, but some exploring pivotal moments in my life, privately and honestly.
You mention fiction that brings out emotion in you. That’s real treasure. First, it points to feelings that are beneath the surface, waiting to come out. Second, you can bring your analytical brain to the scenes that matter and see how experts go about evoking emotions.
On the mirror, that may be a challenge. Start simple. Smile. Tell yourself a joke or a non-threatening anecdote out loud. It’s okay to forget it’s you. What you want is to have a physical way of releasing the brain chemicals that are connected to emotion. Research has shown that, even when you’re not happy, smiling (a smile that reaches your eyes) can get things started.