VIniyoga Basics: Cat/Cow vs. Cakravakasan
Many, many yoga classes begin with cat/cow. It's fine and generally safe, but what tends to happen is that people tend to get really round in their upper back (a shape we are already good at due to sitting in chairs and slouching!) and don't move the low back very much.
Try cakravakasana instead to more effectively stretch and mobilize the low back, and learn to wave through the entirety of your spine!
I can see your blind spots! Book a one on one session with me (in-person or via Skype) for guidance about how to do yoga postures to get the best benefit for you!