Magento2: Cart events

Below Are the list of Events for cart :

1. checkout_cart_add_product_complete
2. checkout_cart_update_item_complete
3. checkout_cart_product_add_after
4. checkout_cart_update_items_before

5. checkout_cart_update_items_after

6. checkout_cart_save_before

7. checkout_cart_save_after
8. checkout_cart_product_update_after

For Use of each refer this url - https://cyrillschumacher.com/magento-2.1-list-of-all-dispatched-events/

You probably need one of these:

checkout_cart_product_add_after
checkout_cart_update_items_before
checkout_cart_update_items_after
checkout_cart_save_before
checkout_cart_save_after
checkout_cart_product_update_after

Have a look at this.

https://www.mageplaza.com/magento-2-module-development/magento-2-events.html