Instead of focusing on how unfit you are and how long it’ll take to get fit, why don’t you focus on the fact that you are lucky that you have the option to run?
Be grateful that you are healthy, that you have two legs that still function as they should. Your body might be unfit and a little weak but you can make it fit again. Not everyone has that option.
So be grateful and appreciate what you’ve got because you might not have it forever.
The best way to appreciate your body is to move it regularly while respecting its current limits (that means don’t do anything that is uncomfortable or hurts – it needs to be enjoyable).
So start where you are, appreciate what you’ve got, say thank you with every step you take and before you know it your body will be fit!