My account(s) keep logging me out...

I have two accounts. The first one is the one I first came up with, and it was working fine until a week or two ago. It kept logging me out, and everytime I wanted to comment on something, I had to sign in again.

So I made a new account, thinking my first one didn't work or something. The segundo one worked, but now, it's logging me out too! Not as much as the first one, but it still logs me out!