Logged out of my metamask

I have my metamask on the Firefox browser. I logged in and then opened another tab and went to uniswap.org. I selected the one of tokens I had on the first place of the swapping box, on the 2nd box I selected Tether. Then out of the blue I got logged out of the metamask the browser tab just closed off on its own. I didn’t realize what caused this to happen. This has happened once before too.

Can anyone please help?