I think there's some evidence for this, and it's consistent with my experiences with myself and what I've seen in others.

It's basically the idea behind the motivation to change literature, that there has to be some point at which the person has to be on board and interested in the change. It may be the desire to change isn't a discrete thing, that something builds over time, and we just become conscious of it at a particular time, or only remember certain moments, or whatever.

There has to be an opportunity though as well, which is another point people get tripped up on and why they lose motivation. Even if someone wants to change, if they don't perceive it as being possible for whatever reason, correctly or incorrectly, the desire for change doesn't have an outlet. It may rise to consciousness and then be immediately quashed because there's nowhere to go.

A lot of the time I think that's the bigger obstacle; it's not being aware of some desire to change, it's having some sense that the change isn't possible or that they don't know how to go about it, which amounts to the same thing.