Searching for birth grandmother

I’ve known most of my life that my mother was adopted by her birth uncle, and that she never knew or cared to find her birth mother, but now that she’s passed, I've been thinking of looking for her. I don’t know where to start. I can’t ask my grandparents either seeing as they both have passed on, and I never met her birth father, he passed away when I was born, so asking relatives for help wouldn’t work. I just don’t know where to start, so any advice would be helpful.