A commmon issue when using GMail, is constantly having to login. You need to Whitelist some tracking cookies. Here’s what you need to go to stay logged in.
- expand the Google website
- look for any red colored cookies
- highlight the NID, SID and SIDCCC Cookies
- right click (control-click) to show the contextual menu
- select Add to Whitelist
Also make sure your browser is not set to delete cookies on quit!