Walking is a very good start, yes. And start slow.

When you get high at night, go for a walk. Night walk is lovely.

Also whenever you think about it, stand on one foot, sounds odd but it’s good for your body. Little exercise breaks, go up the stairs and back down a couple of times.

Mostly I want to say - building a habit takes six weeks. Force yourself every day for six weeks. After that it gets easier because you will feel better on a day you exercise, than a day you don’t, and because you will have found the time of day that works. Habit works a lot better than willpower, but you have to power your way through those first few weeks. Commit to six weeks of daily something. Push ups, walking, whatever.