Motivation is one of the keys to productivity, yes, so getting your motivation aligned with what you're doing is hugely important. That means understanding your goals, from big picture ("here is why I need a job" and "this is why I am at this job") down to "this is why I'm doing this task."

More here: https://codewithoutrules.com/2017/08/03/stay-focused/

I've written a book about how programmers can get to a sane workweek, and one of the chapters is about how to increase productivity. It builds on the above link, but has other techniques as well. If you read the excerpts (https://codewithoutrules.com/saneworkweek/) one of the them is about a specific technique to deal with what happens when you do get unfocused and wander off track.

Probably not what you're looking for but it works for me. If you're physically able, take up running. It doesn't have to be far or fast just getting outside is enough. Listen to an inspiring podcast or audiobook while you do it ("how I built this" is my favourite). As extra motivation to get out, I don't allow myself to listen to that when I'm not running. Running is really time efficient. HIIT is also good for 20-30mins of exercise but it doesn't work for me because I can't listen to a podcast and hear the instructions.

When I'm back at my desk I'm far more productive & energised. I make it a daily habit and leave all the kit in the same place so it's easy to do it on those "off" days.

Have a go at the pomodoro technique.