I don't feel nervous looking at people, but I am cautious not to look for too long or stare, because I don't like to draw attention to myself, and also you never know how the person is going to react when stared at.

I don't normally make eye contact with everyone I pass by, only if the person somehow raises my suspicion or curiosity when I spot them from a distance.

I think that to me the eye contact thing is kind of a "primal instinct", I think I subconsciously try to quickly study people to get that "first impression", maybe find out what they're up to or if they're friendly or hostile.