Mine does the same everday when I first check my mail.
It is my ISP. I checked with them.
I turn off my PC every night so a new log in every morning.
They have their own email so I am logging into their mail with Outlook. I could use theirs direct and stay logged in all the time I just don't like their format.
So I have to log in with Outlook.
Once a day is sufficient though if it drops the connection I have to log back in.
That is a very rare occurence with my ISP though.
I leave Outlook open all day though to keep the connection.
If I close Outlook I have to log in again when I want to check email again.
Sounds like they are dropping the connection so you have to log back in.
My experience anyway.
Mike