I use the "dog method" for cardio. Dog looks expectantly at you and asks to be walked/ran. Dog whines every time you put on shoes. Dog gets weird if not walked/run regularly. Pretty simple motivation! (Dog can be borrowed from neighbor if you don't have your own. You might even get paid for this service.)

Otherwise, I make it part of my schedule. I say, okay, I'm hitting the weight room after work on MWF, and so I won't be home until 6:00 and that's just the way it is. Like brushing my teeth or doing dishes or something else very routine. It's just on my schedule and so I do it.
I also find that if I just promise to do it for five minutes, and then I can quit if I want, that I have never wanted to quit. The instant I'm warmed up, I feel great and want to go on.

HTH!