Reflections. I think it stems from a clip of a horror film I saw as a child (classic scary thing standing behind you in the mirror type scene). In my room I only have a small mirror that remains hidden in a drawer until I need it. When I brush my teeth I have to make sure the bathroom door is closed because seeing the dark hallway behind me in the mirror makes me panic.

Also looking at a dark window in a bright room, as a child, I used to have reccuring nightmares about walking up to the big sliding glass door leading to the back garden. It'd be pitch black outside and because the light was on inside I could only see my reflection, nothing outside. Then I'd crouch in the corner (unable to control myself despite knowing what would happen) and see a gaunt, pallid face staring wide-eyed at me through the window. We'd just stare at each other, unmoving for a few moments before I'd startle awake.

To be fair I'm also scared of looking outside the window at night even if the room is dark as well. Something about the streetlamps and the patches of darkness between them brigns to mind horror films/games and I'm scared I'll see someone standing still and staring at me.

These are just the unusual or specific ones, I'm scared of a lot of things: bees/wasps/hornets, open water, literally my own shadow sometimes, the dark in general, being chased (particularly in an open field or somewhere that's hard to hide/escape. my first panic attack was during a game of tig when I was 10), old porcelain dolls, small spaces (that I can't easily get out of), sitting in a window seat and someone sitting next to me (blocking off my exit), plus many more.

Probably wrote a bit too much haha sorry

TLDR I'm scared of a lot of things