When did you first notice this issue started to happen? Did it happen after installing/uninstalling any internet security software? It could be left over firewall driver causing issues, many antivirus/internet security are notorious for leaving behind drivers after uninstall.
Can you re-call when this started to happen and what steps you did on your PC that lead up to it?
It could be a number of causes either that be:
1. Your PC / User fault.
2. Your Router/Modem .
3. ISP fault.
Do you have a second PC in the household to use? Does the network connection work fine on other devices but not yours? What about Wifi connection with a smart phone? When the connection drops out with your PC does it also drop out on other devices connected to the network or is the issue just isolated to your PC only?
Until we get more information. Try this small free utility then restart your PC. [
Download]