As Scorpiojo has indicated, there are lots of people having similar problems.
You've not told us what device you're using. (A Windows PC or laptop? An Apple Mac? An Android tablet? An iPad? Something else?). Further, you've not told us which browser you're using. It does help to know these things!
However the various tips for dealing with the problem basically come down to:
(a) running a full scan with your anti-virus software ; and/or
(b) running a full scan with Malwarebytes Ani-Malware ; and/or
(c) resetting your browser ; and/or
(d) using System Restore (on a Windows computer) to take the registry back to a time before the problem first occurred.