What’s this berry?
The wild and native Oregon trailing blackberry, Rubus ursinus, looks like this plant. Compare it for yourself with online images, as these photos don't include much of the stems.
The OSU Landscape Plants page has great photos and descriptions: https://landscapeplants.oregonstate.edu/plants/rubus-ursinus
This page from Portland State University may be helpful to you, as well: http://web.pdx.edu/~maserj/ESR410/rubisursinus.html