This is by no means a scary or exciting account but it certainly was puzzling at the time. Even yet I have no definitive explanation but many people on this site have had similar experiences which lends an air of normalcy to otherwise inexplicable happenings.
18 years ago I was employed at a large automotive manufacturer just outside of Cambridge, Ontario. I worked in the boiler room on a 24 hour rotation. Part of my duties was to perform water tests on the various boilers and chillers, which would take about half an hour on each of the eight hour shifts. We worked with at least one other person on "off" shifts and with a few more people during day shift.
Water tests took quite a bit of concentration as you were usually looking for a colour change in the water sample while adding very small amounts of chemical reagent. This is called titration.
One night, at about 1:00 AM, while absorbed in my tests, I noticed in my peripheral vision, my shift partner walk up to me in a bee line from another part of the large boiler room. He stood about three feet in front and to the right of me, beside the water testing counter. I could not look up to talk to him as I was concentrating on a titration end point. He stood there patiently and silently waiting for me to finish.
When I could finally look up at him, there was nobody there. I could not understand it as he was there in my peripheral vision but he certainly was not there when I moved my head to look at him directly. I was not scared but I sure had a lot of questions and self doubt about what really happened just then.
A week later I was on night shift again and the same thing happened as it did the week before. I believed that a real life person had walked up to me and was waiting to speak to me. When I looked up, you guessed it, nobody was there.
This happened numerous times but only on night shift, never on day shift or afternoon shift. But as it was not scary and I was a fairly new employee I did not mention it to anybody for fear of being ridiculed.
After a couple of months of this happening fairly regularly I was on night shift with "John". While sitting in the lunch room we were talking about various things when he abruptly changed the topic and asked me if I ever saw a person walk up to me in my peripheral vision and that when I would look up nobody was there. I eagerly told him, with some relief, that this happened most of the nights that I was there. He told me that this happened to him at about the same frequency.
It must have bothered him more than me though because he proceeded to produce a newspaper article, that he had neatly folded in his breast pocket, that spoke to this type of occurrence. In short the author, a medical doctor, wrote that when we are alone we are in an unnatural situation where we are starved for seeing people so our brain manufactures them and we then see people in our peripheral vision to make up for our loneliness. He even had a medical name for this type of event (which I fail to remember).
I found this to be nonsense and told him so. This never happened to me in any other place where I was alone nor did it happen at that factory on any other shift but night shift even though I was just as alone on afternoon shift. It also happened to him and to me, only at the water test bench. He insisted that the doctor knew better.
I believe that he took comfort from the "normalization" that the doctor's diagnosis provided but I still believe that what happened was paranormal.
After these happenings were outed, so to speak, I asked others if they had experienced this but they had not. One person, though, told me that as the factory was built they found quite a few buried bodies in what must have been a long forgotten and unmarked graveyard. The bodies were removed to another location and work on the factory recommenced. This graveyard was in the area that became the boiler room. I am not sure if the disturbance of the graves caused my peripheral visitations or not.
Not long afterwards I left that job and moved on to other places of employment but I have never had a repeat of that type of occurrence.