Google is automatically redirecting to unknown websites

Reset your browser and see if it fixes the issue.
If it does not, check your addons and see if there are any third party addons. You have to disable the addons and see if it fixes the issue.
If the issue persists event after the removal of addons, you have to check the programs and features control panel window to see if there are programs that might lead to such problems. Those could be toolbars, players and fake tweakers. If found, uninstall the programs, restart the system and see if it fixes the issues.
Change/remove startup items using Task Manager if the operating system is Windows 8 or beyond. Or else you have to use the msconfig.
Try using an adware remover such as this or this, and a software such as Malware Bytes to scan the system and remove possible threats and risks.