Internet problem

Your description is vague, but if it is anything on your side, it will be your router (which might be an ISP provider modem+router, if you haven't bought/added a router yourself). Check for firmware updates.

Look for the possibility your activity is causing the problem, like running bittorrent or causing lots of network activity when the problem happens.

If that isn't it, you can try working with your ISP. If they don't have a good idea what the problem is right away, they probably won't be helpful. But as long as it isn't Indian tech support, try their suggestions as long as they are willing to waste their time, too.

The key point in your description is that, according to the error msg, DNS is working, but opening TCP connections is failing, but not 100% (partial load pages).