We had an
issue around two weeks ago with caching that would cause login sessions to last under an hour and fail to refresh, try manually clearing all existing cache/site data for MD because you might still have remnants of that lying around.
If you're still having issues after that, check browser addons/browser config for anything that mentions "history/cache/site data/logins/cookies/session tokens" and make sure you're not accidentally nuking your own credentials. Some browsers (like Librewolf) wipe localstorage on tab close/browser shutdown, and that'll log you out too.