That kind of consistency across multiple nights is what separates it from a one-off brain glitch in my opinion. Once, maybe your mind's filling in gaps. Three nights in a row at the same spot? That's harder to dismiss.
Did it have any kind of defined shape or was it more like a mass of darkness? I've read a lot of accounts where people describe shadow figures as distinctly humanoid, upright, sometimes with a hat even (the "hat man" thing comes up constantly). Curious whether yours matches any of that or if it felt different.
Also worth asking - were you in any kind of heightened stress period at the time? Not trying to debunk you, genuinely think there might be a link between emotional states and how often people encounter this stuff. Some NDE researchers have touched on similar ideas around perception shifting when you're vulnerable.
Would love to hear more details if you're up for sharing them.