Cerys, even after so many years of going out in daylight and at night, I occasionally get that uncomfortable or threatened feeling that you experienced.
In my 20’s, before I learned to be more wary, I experienced some really bad incidents, but eventually (more like 3 or 4 years) I learned to relax and not be as jumpy.
One counselor I saw was a combat veteran. He explained that ‘nervous for no reason feeling as something you did actually see, but it did not register with you consciously at the time you saw whatever it was. Your subconscious finally or partially worked it out and started sending out sos signals to your conscious.
These triggers aren’t always sights, but can be sounds or smells also that you don’t register until some little neuron of memory makes the connection and starts the response, knowing it or not.
A few times that I have been out and about since those bad experiences in my 20’s, I have gotten an odd feeling from something I could not figure out. I have caught myself checking store window reflections as I pass by to see if someone might be following me. I also have stopped and looked to try and calm myself, sped up my pace, and generally tried to leave the area. Once away, the feeling will finally pass, but it can still be a little unnerving when it happens.
Things like that happen, but please don’t ignore them either. Enjoy your outings but be careful.