Being logged out each time site is navigated around.

I’d like to know, is there a way in which the user can be only be logged out of the site when they physically log out of the page using the log out feature?
As at the moment im being asked to log in each and every time i try to access my account page, after having gone to my other pages(non-account related) then back to my account.

It never used to do this, so im wondering if this was a setting or feature I had enabled/disabled within the theme?

Thankyou.