Store Checkout Settings submenu item allows you to hide unnecessary checkout form fields. See screenshot.
Store Checkout Settings - Terms & Conditions
You can add a checkbox to cart page for "Terms & Conditions" agreements (GDPR, Age restrictions, etc.) that hides "Checkout" button if it is not checked. To do so please navigate to Store - Settings - Checkout - Enable terms checkbox and click save.
Once the visitor checks Terms & Conditions, they will be able to proceed to "Checkout".