Any hints which adons you got?
I'd start with UI changers like LUI, BetterUI, BanditsUI etc. first.
Disable them and see if it's gone.
Else search for addons with "timer" or "playtime" or similar.


I always do this:
Use Addon Selector to save the currently enabled addons as a profile.

Disbale all addons and check if it's gone: If not it was added by Zos, no addon

Disable the upper half of the addons (you can click the 1st addon and then use SHIFT+click at the middle to disable/enable all of them in between. Sometimes it does not work properly, especially if "Votans Addon List" is enabled so better check that all are disabled).
Relaod the UI and see if it's gone, if not, re enable the upper and disable the lower half.

If it's gone, re-enable the lower half and do the same again within the lower halb, disable the upper lower-half etc.

Another idea:
Move your mouse cursor above the control shown and type into chat
/script d(moc():GetName())

If you are lucky the name of the control you had the mouse above is shown. If it's GuiRoot then you are unlucky as this is the normal Graphical userInterface and does not tell you which addon added it.
If you are lucky the control name shown is something like MyAddonName_Timer1 and you see the addon name that way.
Maybe the addon name is abbreviated but it should help you to find it via a text search in your addons folder (you can use free tools like Notepad++ to search the whole live/Addons folder for texts e.g., or the windows search).

Oh nice, automatically enabled features like this are annoying... Glad you found it