You got used to being unmotivated. As others mentioned before, you need a bit of discipline. But discipline alone is not the point. I would recommend using productivity techniques. Checklists might be to easy but getting things done or eat that frog are great methods. At the beginning it´s hard, but as you constantly use them, it will become a habit. And, for me, it´s a great feeling and boosts my motivation when I see what I have already finished or when I´m able to set one task to "done". I personally use getting things done and it really helps to stay focused, you can also use "time blocking" to concentrate on your tasks or to make sure you got time to do nothing at all.

If you need more info about all the methods, have a look at our blog, there are articles about many possibilities to boost productivity and enhance your motivation: https://zenkit.com/en/blog