To answer your question: you don't need to start with one type to move onto another. Jump in to anyone that you like. But I would strongly entourage you to start with a local beginner's class. Start say once a week, and if you aren't very flexible you might be a bit sore for a few days afterward. Sometimes you can get them quite inexpensively at a Community College.
You can also supplement with things, like, The Biggest Loser with Kinect for the Xbox 360, and it has some Yoga in it, and even Yourshape on the Xbox/PS3 and My Fitness Coatch for the Wii all have yoga routines. And even DVD's and video workouts.
But do yourself a favor and take some classes in person, so you don't develop bad habits and end up hurting yourself. Be patient, it took a while to get in the kind of shape you are end now, and it will take some time to work out of it.
It's used to help many people with back and other problems. It's a great ancient practice.
And it's way to early to be worrying about being 'too thin.'
Zappykins
PS good luck!







