To get motivated when you aren’t, you first need to find the motivation to motivate yourself.
I recognize that sounds like word soup or an antimetabole, and it kind of is. At the very least it suffers from the problem of infinite regression. After all, how can you get up the motivation to motivate yourself if you don’t have enough motivation to be motivated in the first place? Turtles all the way down.
Thankfully, there are some forces that are a lot more powerful than our conscious minds. Forces we can use as an external push to provide a solid foundation for all those turtles and kick start some motivation without effort on our part.