Code after do_shortcode not working

I am trying to create a custom function in my child theme’s functions.php file.
The function executes when a webform is submitted and then I am running a shortcode to save the form’s data and transferring user to Paypal building url of all posted values of the form

Now, the do_shortcode part works fine but it doesn’t redirect to paypal

Please help!

function process_my_form(){
    if( isset( $_POST['formname'] ) ){
        // process form and redirect
        
        $vars = array(
            'cmd' => '_xclick',
            'currency_code' =>' CAD',
            'country' => 'CA',
            'item_name' => 'xxxx',
            'custom' => $_POST['custom'],
            'amount' => '199',
            'first_name' => $_POST['first_name'],
            'last_name' => $_POST['last_name'],
            'address1' => $_POST['address1'],
            'city' => $_POST['city'],
            'state' => $_POST['state'],
            'zip' => $_POST['zip'],
            'email' => $_POST['email'],
            'phone' => $_POST['phone'],
            'quantity' => $_POST['quantity'],
            );
        echo do_shortcode( '[cfdb-save-form-post]');
        header('Location: https://www.paypal.com/ca/cgi-bin/webscr?'. http_build_query($vars));
        exit;

    }
}
add_action( 'init', 'process_my_form' );

Thank you