That sounds like some spyware and/or adware. Download Malwarebytes and run a full scan and delete any threats it finds. Also, on all of the web browsers you have, clear your history, cache, and cookies. If you recently installed any program that might be shady, uninstall it. Because even if your Malwarebytes removes the threats, the program might try to re-download them.
Unfortunately, its hard to know exactly what program(s) could be causing this. Sometimes "free" programs will also download other programs while you're installing the main one.