There is no definitive answer to how often you should submit a sitemap to Google as it depends on various factors such as the size and frequency of changes on your website.
However, as a general guideline, it is recommended to submit a sitemap to Google whenever you make significant changes to your website's structure or content. This could include adding new pages, removing old ones, restructuring your website, or updating content.
Additionally, it's advisable to regularly monitor your website's performance and crawl errors in Google Search Console. If you notice any indexing issues or errors, submitting an updated sitemap can help Google discover and index your website's pages more efficiently.
In essence, while there is no strict frequency, you should submit a sitemap whenever there are significant changes to your website and as needed to optimize the indexing process.