i've never done an actual yoga class but i've tried body balance and pilates.

i didn't find either of them relaxing. body balance mainly consisted of trying to bend myself into painful/achy positions (apparently my body doesn't like sitting cross-legged) and trying not to fart. and the pilates lady went on about doing the right kind of breathing so much that i was actually worried i was going to get it wrong and she was going to tell me off or smthg.

i guess i just find it easy enough to relax in front of the telly, or with a book. if i'm going to do a class, i want it to be something where i get a sweat on and feel like i've burned some calories.

Depends on what kind of yoga. i find slow, hatha yoga very relaxing and will get on the floor and do some poses to relax & stretch when i'm in pain.
a lot of it is breathing and becoming aware of your body.