Reboot router to fix the lose internet connection issue, but only good for 5 minutes

Recently I encountered the issue of losing Internet connection: the signal light became orange on the router. And I found the model seemed working fine as all the signal lights on it appear normal.

Yesterday morning (about 8:50am CT), it happened again. I then pulled off the power cable of the router, waited about a minute and then put it back on. The router reboots, and everything went back to normal. But it only lasted about 5 minutes. The internet signal light on the router would become orange again and I had the same issue!

I have seen this a couple of times. The only longer solution would be reboot both my modem and router. So my question is what is the problem here? Is it only from router or my modem, or I need to take care of both?

PS. Today, this happened again at almost the same time.

I tried to look for clues in the modem log. It shows a bunch of T3 and T4 time out. Also the time became 1970/1/1 for a couple of times.