Try the following solutions one by one if your Internet keeps disconnecting:
Test on Other Devices
First, check whether the Internet disconnection issue is limited to only one particular device it also occurs on other devices. If the problem occurs on different devices, such as PC, laptop, tablets and smartphones, it should be fixed accordingly.
Unplug & Replug Cable
Try unplugging and replugging the data cable of your modem/ router. Check if the problem persists.
Replace Damaged Cable
If you’re using a wired connection, check the quality of data cable. Power off your modem/ router first, and then remove damaged cable and replace it with a new one.
Switch off and switch on your modem/ router and try connecting the Internet again.
Reset your Wi-Fi Data Card
If you’re experiencing problems with a Wi-Fi connection, just restore the system defaults. To do so, remove the back cover of your Wi-Fi Data Card and then press & hold the small Reset button for a while. It will automatically set up default configurations.
Contact your ISP
Contact your Internet Service Provider for technical support. There may be other issues from their side.
Reinsert Network Card
Power off and unplug your PC, open your desktop computer’s cabinet, remove the Network Cable. Wait for some time, firmly insert your network card into the slot.
Reinstall Network Card Drivers
Check whether you’re missing an important network driver update. Updating can be performed in two ways – First, accessing the ISP’s website > Downloads section; or second, using Device Manager > Expand top node > Expand Network Device > Right click > Update driver software.