system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do we grab our chest when we are startled?

"Oh my God you scared me"
gpt
I just did a quick google a managed to find a little info that may help

The responses of people to a startling incident vary widely between the fight, fly, or freeze options. When startled, people may wildly flail their arms, or suddenly raise their limbs in protective poses, or duck to avoid an object. The shocked and surprised often back pedal, jump back, or run away from a frontal stimulus. They may clutch a rail, or furniture to prevent from falling. Their knees may buckle, causing them to fall down. They may drop the things they are holding.

They may freeze, or instantly follow orders. They may clutch their chests, faint or even suffer a temporary heart attack The aggressive ones may curse or throw things at the object, which startled them, or strike out at them.

So it sounds like it clutching your just is a response you hafe in order to protect your torso.