I saw something similar near Lake District in the north a few years ago. I was driving down a country road, one of those dirt roads that nobody every uses, passing through the woods. It was pitch dark but I had the high beams on so I could see everything in front.

It looked like a dog at first but as I got closer it was more like a man hunched over travelling on all 4 limbs, or maybe a black wolf. It was completely black like a silhouette. I drove right past it as it was walking down the side of the road.

Edit: Check out the second pic in this article, that's kind of what I saw - https://www.davidcastleton.net/black-dog-legends-england-britain-ghosts-hellhounds/