Use Shipping Session
Go to System → Settings → Checkout
When enabled, shipping quotes are stored in the customer’s session to avoid repeated recalculations. Quotes will only update if the cart contents or shipping address change, which can improve performance and speed up the checkout process.
Note: After changing this setting, it is important to clear the browser cookies to start a new customer session. Otherwise, previously cached delivery methods may remain in the session and not reflect the updated configuration.