Flex Circuit Gym
I'm a 37-year-old, overweight, out-of-shape (newish) mom and I know how you feel! I worked out at Flex Circuit Gym on Piedmont Avenue for years before I moved to Berkeley last month. I loved that gym because it was very welcoming and inclusive: you see every shape, size, and age. There's a public parking lot about a half block away or people also park in the Wells Fargo parking lot at night, which has ample parking. Good luck with your search!
I would recommend Flex on Piedmont. Definitely not an intimidating gym. Lots of people of different ages and ability. It’s street parking but it’s usually not hard to find