That sounds like automatic braking. There usually isn’t a way to turn that off, as it’s a safety feature. I agree it can be abrupt when it kicks in (i.e. it slams the brakes). It usually only works at low speeds (20mph or less, for example).
I often encounter it when the car in front of me turns off the road into a driveway or another road. It will slow down to do that and its backside is sticking out in my road slightly, but it’s not stopped. It’s moving and turning out of the way. I would slow but not brake, but auto-braking will slam on the brakes even though I’m nowhere near clipping the other car. It “sees” the other car even when it’s outside of my lane. Very annoying!
But I have had a few times when cars in front of me stopped unexpectedly and I didn’t realize soon enough, but my car automatically stopped, which saved a potential collision. So it can be useful!