For myself the easiest way to motivate myself is to set a target. I have a main one for 2017 to knock 2 hours off the Marmotte time I did in June, that is why I went Keto.
so if just starting exercise, forget your weight, set yourself a target
- walk a mile in 15 mins
- slight jogging for a mile
- gentle 10 mile bike ride
- 1 plank of 15 second
- lifting 20kgs
Whatever floats your boat, aim gentle then once reached, add a bit more length/time/weight etc onto the target. Make them realistic, make them achievable, The sense of hitting targets is far greater motivation than anything else.