I'll start (Background: I run 3/4 times a week, hot yoga once a week and swim a couple of times)
What does motivate me...
Numbers I love my fitness tracker and my Strava running account. I love seeing how many miles I've clocked and any improvements in speed etc. I'm addicted to seeing how exercise over time lowers my resting heart rate and clocking up my active minutes.
My shower/bath/lazing around after I do most of my running in the morning and I love getting in the shower at 6.15am knowing I've already clocked up 5k that day. Likewise, I love drinking coke and eating peanuts in the bath after a long run. Or the lovely all body acheyness after a swim or yoga. I am very lazy, mainly a stationary kind of human, but the exercise lets me feel like I've earned my hanging out doing nothing.
Exercise itself The quickest way for me to get exercise mojo is just to do some exercise. Just a teeny run, or a swim, or a class, and I'm back on it and planning my next exercise. I reckon my real hobby is making fantasy exercise schedules, and then in real life I'm just doing the bear minimum to allow me to carry on these fantasies!
When I'm exercising, I feel like everything is pointing in the right direction and I've got a life a bit under control. I'll eat better, drink less, go to bed earlier. Sometimes it's hard to be a patient parent, good employee, considerate wife/daughter etc. Rather than over thinking all that stuff and trying to find solutions, I can just do some exercise I am automatically a nicer person. With less hand-wringing and over-thinking.
What doesn't motivate me...
Looking better, getting in shape etc I am proud of the fact that I am better shape now than I used to be, but that would never motivate me to get out the door. It's too abstract and long term.
Enjoyment of the exercise itself I know some people who enjoy running, but really I don't. The best I can say about running is that most of the time I don't hate it. Swimming, well, that's largely just boring. Yoga I probably like the most out of what I do, but even then there are times, like at the start of a Bikram class, when I think about all the stuff I'm going to have to do in the next 90min and I am filled with dread.
Okay, over to you guys....