When I moved into my first apartment in Los Angeles, I kept getting the feeling I was being watched. I didn't like sleeping with my back to the door and didn't know why.
I felt safe when I was on the phone with someone or had company but I never felt totally secure when I was by myself. I tried to let it go but I couldn't -- I just got lots of weird vibes.
One night, middle of the night, I saw a kind old man with glasses on, a little stooped over walk into my bedroom; he was a bit surprised I was there and I just said "It's fine, everything's fine." He said "Oh, O.K." and looked apologetic and backed away. When I woke up, I thought it was the most bizarre dream. Got up, went about my day.
I ran into my landlord the following week and asked him who had lived in my apartment before me. He told me some girl lived there for four months before me, but before that it was empty for a long time. I asked him why and he mentioned the previous owner of the building had lived in that apartment before going to the nursing home where he died.
I asked him to describe the guy...and he did and I turned white.
TL;DR Ghost of the previous occupant of my apartment visited me; I thought it was a dream.