Getting “shocked” or “startled” when you run into people you know

This always happens to me. Like at work. If I’m walking in the hallway in our office, minding my own business, thinking about work stuff or random stuff….Then a coworker shows up, and I feel startled. Lol. Even though I’m at work, and this is where all my coworkers are. Yet, I still feel that “startled/surprised” feeling. Like I got “caught”, like “look! There he is! It’s uncbluedevils! We got him!!!” Why am I like this? lol