Start off with short day hikes. Hike with friends. Try Via Ferrata - ascending mountain cliffs with ladders and iron walkways. Go for a multi-day hike and camp out overnight...
Develop a daily practice. Take some online classes - you can do these anywhere - even on a beach. Go on a yoga retreat. Try aerial yoga where you are suspended from the ceiling.
Go from Couch to 5K and try a Parkrun. Join a running club. Sign up for cross country or try a trail run. Train for a marathon or take part in a relay.
Walk to work. Ask your boss for a standing desk. Take the stairs at every opportunity. Get up early and exercise first thing in the morning. Try a new sport. Sign up for a charity challenge.
Take part in a Zombie race. Try paddle boarding. Discover Tai Chi and practice in your local park. Learn how to canoe. Go potholing. Go for a night hike and tell ghost stories.