This problem can be virus that is in the system, I advise to take in an autorirazed or if you have knowledge resinstall windows.
In the last case it may be the keyboard that has bad contact and ends up tightening shortcuts without you wanting those like the windows.
Check your computer to see if there is spam in it, usually facts that occurred directly in the browser or is some Extension installed or spam as I said. Use an antivirus and uninstall the chrome extensions.