Some of the main reason why a laptop could keep freezing could be due to corrupt operating system files or overheating. Corrupt operating system files could be caused by malware or viruses that you can download from sites. Watching movies, videos and playing games are also major factors that cause laptop to freeze. Check out http://computerfreezes.net/laptop-keeps-freezing-the-3-most-likely-causes-and-how-to-fix-them/ for more tips that could cause laptop to freeze.
Do you have virus protection? Is there a date when you did not have this problem? You can reset the computer to the earlier date settings and see if that helps Otherwise call mfg for tech support or drop at cheap repairman for estimate