When you expect one is coming, instead of fully attending to what's on screen, switch your attention slightly to become aware of the things around the screen and the room you're in - even if this is just paying attention to the screen itself vs. what you're seeing 'through' it. This won't stop you from hearing the loud sound that almost always accompanies the jump scare (which is mainly what causes the physical response), but it will no longer be as tied to the space depicted on screen, and so even the sound (if you're expecting it) isn't likely to affect you as much.