I have this problem too (((((((BlackPup))))))))) A lot. Sometimes I find it's not until the end of the day that I'm actually able to crank through my work. I think it has something to do with feeling pressured to get something done before I leave work. I often work best under pressure (time pressure). And I find that I accomplish more in the last 2 hours or so of the day than I do the rest of the day.

I'm definitely not recommending this as an effective way to work though. It's just something I've noticed about my patterns. Lack of focus sucks!! I'm sorry you're struggling with this too. Have you tried breaking down what needs to be done into small chunks??? Perhaps that would help?