My motivation levels for training are about on par with my motivation levels to do anything else like brushing my teeth, having a shower, eating, wearing clothes, etc.
I suspect that the people who say: "I want to get fit but just don't have the motivation" make it out in their minds that exercise is something huge and overwhelming, when it really doesn't have to be. Perhaps they see it as some impossible feat, or as something that's just impossibly boring, but in any case the people who whinge that they just don't have the motivation probably set a standard for exercise that makes it demotivating, because that standard is either unachievable or or not something they'd actually like to achieve. Of course, I'm only speculating here, and I guess there would be other options available, but this seems to be a fair deduction based on my observations.
Like I said, it takes about as much motivation for me to go to the gym as it does for me to literally go anywhere or do anything. Sure, I need a bit of extra motivation to push myself to or near failure, but to just show up and challenge myself a little? That's motivating! To constantly push myself into the ground while training would be demotivational, and to "train" at such a low level of effort that to call it "going through the motions" would be implying too much would be demotivational. But to find something I enjoy and that's at a challenging but very achievable level, that's exciting, and has me looking forward to the session, and leaving the session feeling really good. If you look forward to something, enjoy doing it, and feel like a king once it's done, then you're not going to need much motivation outside of that.