W3 Cache is not working

I’ve installed W3 Cache but it seems it’s not working. Actually the performance decreases and sometimes the site shut down. I browse the site and when I see the source code of the pages I can read the footer of W3 Cache “Performance optimized by W3 Total Cache” but every reload the date time of the cache is changing as it has creating another cache file. (When I do it I am not logged in).

Someone could help me on this issue?

Thanks!