We get that feeling for a very good reason. It’s our intuition telling us something our instincts already know. Many people don’t get it and are conditioned into telling themselves “it’s probably nothing” because they don’t want to look silly in public. It can lead to paranoia, if you’ve been in enough hairy situations, but most of the time you’ll want to listen to that intuition and do something about it as soon as you get that feeling.