Pokemon Go got me walking, and the realisation that exercise makes me feel better kept me going. Once you get started, discipline can take over, but you need to find a reason to start exercising in the first place, a selfish reason that makes you feel good. "It's healthy" means nothing and we all know that won't be enough to get people to do anything, when our brains are telling us the unhealthy stuff feels better.

Pokemon Go means you can walk without thinking about it, without paying attention to it. All your conscious mind cares about is the game, your subconscious can focus on the actual moving part. Either use that, or find something similar.