Starting exercised

try walking. Start with 10 minutes and increase after 3 days by 10 minutes. After 3 days another 10 etc. till up to 30 minutes. Take 1 or 2 days off a week.

I second walking. I've been walking for over a month now, in a heated corridor so no tightness from the cold, and even flooring. Swimming/walking in a pool or an elliptical would also be good exercises.

Remember to listen to your body! It'll tell you when you're doing too much, whether it's too long a walk, too fast a walk, or too many days in a row.