Look in System Preferences : Users & Groups and select the Login Items tab. Select anything in there, and click the [-] button to remove them. Exit System Preferences and reboot your Mac.
Download and install the free Malwarebytes anti-malware tool, and run it. Does it find anything (malware) that it offers to remove? Many of us also use this product. Occasionally, it will fix things without notification too. Does your issue continue after running Malwarebytes?
Malwarebytes is a 14-day full featured trial, during and after the trial, you can run it interactively to check for malware. There is an optional subscription that enables the real-time checking that is on in the trial.