My router's Ethernet light turns solid orange suddenly from Green and the internet access gets lost for all connected devices.

But it is not a problem from the ISP side as when there is a issue from ISP side, internet connectivity is lost for a day or so (Ethernet light gets solid orange for a day or two). Though I contacted ISP but it was okay from their side.

Here for sometime router works fine (solid green Ethernet light) then suddenly turns solid orange again after a minute or so back to green and this happens frequently from somedays now.

I've tried rebooting and resetting the router.

Can anyone provide with some diagnosis and troubleshooting steps, also how to rectify this issue.