Three nights in a row is not random, thats when you know something's actually there and not just your eyes playing tricks. Shadow figures that repeat like that tend to be tied to a location rather than just passing through - at least thats been my experience with the cases I've followed closely.
Does it have a defined shape? Like does it look roughly humanoid or more like a blob/mass? That detail matters a lot when trying to figure out what you're dealing with. Some of the more credible poltergeist reports I've read describe a shadow presence showing up right before physical activity starts, so worth paying attention to whether anything else feels off in the house.
Would love to hear more details if you're comfortable sharing. Others here have had similar encounters and might recognise patterns you don't even realise are significant yet.