My dog, 5yo spayed female rescue, who I've had for almost two years, has developed a strange quirk. For the first year or so, we would sleep in the bed, and usually she would lean against me, which helped us both sleep. But the last few months, if I was touching her hind quarters and moved while she was sleeping, she'd sometimes jump up growling before realizing it was me, and then run off the bed. Sometimes she even does it when awake.

I'm not really sure what this behavior is or why it started so suddenly. She's not injured and the vet has not seen anything wrong with her physically. It seems to be a trigger from her time on the streets, but I'm not sure why it's "flared up" lately.

Any thoughts on how to calm this response?