Whatever motivates you to get back to riding will make you wonder why you waited so long. I've been bike commuting for years, but only on days when it's dry out and my schedule allows. Which usually means not riding outside for a couple of months during the winter. It always is kind of painful when I resume, but the pain fades pretty quickly as I get back into the habit.
I got my annual cold shortly after the first of the year, and am just now starting to feel better. I rode yesterday and today, and the ride in yesterday was brutal when you factor in the couple of weeks off I had, the illness, the cold and the maintenance I've been putting off so I can keep riding. But the ride home was much much better, and I knew I wouldn't have felt this good if I drove.