That sounds like betaflight has something the wrong way around, so when it notices a slight tilt, it powers up the wrong motor, which makes the problem worse and causes a run-away feedback loop. There are several things you could have set wrong.
Check that your quad detects motion correctly (i.e. the picture in beta flight moves as you rotate the quad).
Check the motor direction matches the image on the first page of BF.
Check the channels are mapped correctly on the receiver page. E.g. the aileron channel moves when you move the right stick sideways. There's also another moving picture of the quad here, where you can check it moves in the right direction in response to the sticks.
Check the motors are connected to the right place, by testing them on the motor page.
If that doesn't fix it, find some of the many 'how to set up beta flight' videos and work through it. It's a lot to learn at first, but you do get used to it.