This is difficult because the closest leaves are not in focus and sun-lovers growing in shade can appear quite different from their sun-growing siblings. Consider this a maybe-id, and you can compare the plant in person more closely to see if you think it is a match.

Cotoneaster lacteus. It is commonly grown in SoCal and the leafs and veining, petiole angles and lighter-colored newer stems resemble the plant in your photo. I have seen them planted in part shade, but volunteers are not uncommon, and probably the route this one originated (if that is what it is). There are quite a few cultivars, but I don't use cotoneasters in landscapes frequently enough to separate those characteristics in the field.

I took a look, it does look similar, but I don't recall this plant ever blooming or showing berries. The shade used to be full on, it's now partial given that we trimmed some major pines. When it was full shade, I didn't even notice the plant, so maybe it will bloom now.

I also thought Cotoneaster. I've had a few volunteer over the years. Some under other shrubs so they did not flower and therefore did not berry.

Thank you both! It's listed as invasive so I will end up pulling it out if berries arrive... as I presume that birds eat them and spread it that way. Till then, I like the color of the leaves, and it doesn't look terribly out of place so it can stay. : )

Also ----- Interesting that it's from China and a member of the rose family,. I planted the native Toyon nearby (in spot that gets more sun) and Toyon is from the same family.