Frequent browser disconnects

For the past week I have experienced frequent browsing issues 80% of the time I'm online.  I've checked everything I can locally.  I've connected directly to my cable modem & had the same issue.  When it works, it works well & I get 24 mb download speed according to speedtest.net, but it fails frequently with error "Webserver Not Found" or a similar message.  It's like there's a loop on my segment & the packets get redrected for a while, then it clears up for a minute, then fails for five minutes.  I never drop connectivty to Cox, & the lights on the modem look good.  Any help would be appreciated. Thanks