Like Mommamia, I have developed (in recent years) a fear of going over bridges. It is irrational, and I used to LOVE going on bridges. Nothing ever happened to me on a bridge, I just basically woke up one day, afraid of being on one. It doesn’t stop me from traveling, but I also ask my hubby to drive in the center of the bridge.
Many of the fears mentioned are not unexplainable. There are sound reasons to fear lightning, certain bugs, snakes, and MICE (a biggie with me). What is more unexplainable might be a fear that inerferes with one’s ability to live life and enjoy it.