A browser hijacker is currently installed in your system if your startup page keeps getting redirected to search.oz4zufv.com. This browser hijacker will attempt to commandeer your browser search and its search results or sponsored links will send you to malicious websites to get money from you or infect your computer further. It may also prevent you from changing your settings back.
Search.oz4zufv.com is usually installed through bundled software without you knowing. Remove it immediately.