I don't do yoga, but I go to a pilates class every week, which is similar to yoga. I love it, makes me feel really relaxed and energised at the same time.
I can't do all the exercises, but anything is better than nothing! Plus I'm the youngest in the class by about 40years so there's no pressure to be amazing.
Just take things at your own pace, I've been doing it about 3 months now and can manage more and more each week.
Lucinda