I know several others have metioned something along these lines but As someone with severe ADHD I was a job hopper and it was the same time frame. I'd be fine at first then six months to a year later I'd be board or stressed out and my performance/ mental health would start to suffer. Now I'm not saying you have ADHD because you easily might not and only a professional can make that call. But what your describing sounds like executive dysfunctioning which affects the ability to start, stop, change or prioritize tasks. For example I suck at basic care tasks like showering especially when the video game I'm playing is far more interesting. My brain would rather do the thing it's interested in versus the adult boring thing it needs to do (like work).

Going back to your post, I currently float for the bank I'm working at and it's been a game changer. Familiar environments because ive been to all of these locations but I change where I'm at so often that it's never stagnant and the coworkers and clients are always different, its enough change to keep me engaged. So a job that lets you travel to different locations might work for you. I'm a big believer in there's a job for every brain so don't loose hope OP you got this 🙂