Log in box

Hi guys, apologies if wrong forum, just noticed recently whilst im writing up posts, strangely the pop up window asking me to re-log in pops up quite a lot. I understand if your logged in and you don’t do anything it will log out, but when you in the middle of writing posts I don’t get. Is it a glitch? or something else?

The page I need help with: [log in to see the link]