You are not your body. Body just sprang up. You existed even before your body came into existence. You will continue to exist after your body ceases to exist.

Body is just a possession. It receives inputs through its five senses. The inputs are processed in the mind. When the body merely receives inputs and if the mind is absent at that moment, then the inputs are not processed. So it is the mind that exists. It is the existence of the mind that makes me say 'I exist'.

When your body acts, it is your mind that is acting. The body merely attempts to physically execute the decisions of the mind.