You may get Confirm Form Resubmission because of various reasons. Sometimes, it's not even an error and is great for your security. When you take too much time to do a transaction, you may see the error message, or when you are submitting a confidential form. But sometimes, it appears way more often and that is exasperating. It appears when filling Google form, or logging in, or refreshing a page, or going back. There are multiple reasons why this can occur, such as poor Internet connection, a Firewall issue, a glitch in your browser's cache, or something else.