Yeah, sounds like you're hinging at the lumbar spine (bad) when you should be hinging at the hips (good).
Don't try to get too deep at first...keep your back locked and once you feel the stretch go back up.
Don't worry if they are shallow, the ROM will improve over time.
Somehow, I picked the weakest video, but it gives you a decent visual (the guy's a little stiff if you ask me but his back position is safe).