There is not a built-in way to send out an email merge from Gmail.
Outlook is a free email client from Microsoft that can be connected to your Gmail account to send out mail merges. To install G Suite Sync for Microsoft Outlook, follow the instructions on this page: Microsoft Outlook and G Suite Sync for Windows
There are Gmail add-ons that provide mail merge functionality. ITS does not support the use of third-party add-ons because they are not fully supported by Google and also warns that there are known malicious or insecure plugins that could steal your data or compromise your computer.
See Microsoft's web site for instructions on Mail Merging to Outlook. https://support.office.com/en-us/article/Use-mail-merge-to-send-personalized-email-messages-to-your-email-address-list-c49e5cfc-53f9-4ec8-9bd9-1f8f3648f1b7YAMM is a tool to help you send mail-merged emails using your Swarthmore Gmail and Google Sheets (part of Google Drive). YAMM, which stands for "Yet Another Mail Merge," integrates with your Swarthmore Gmail account to allow you to send mail merged messages.
To access the tutorial pages and get started with Gmail email merges, install the YAMM add-on: