Internet Unusable

Hello,

I got home from a week long vacation and found the internet was out, and in the 24 hours since then it’s been dropping out every 15-30 minutes. Restarting the modem will grant me a few minutes of internet access but it quickly drops out and will not work until I unplug the router. So far I’ve done a hard reset on the router with the button on the back, I’ve checked the coax cable and the connections, I went through the guide posted by user EG and checked the signal and power levels, which seem to be within the normal range. This is affecting my devices on WiFi as well as my computer which is connected via Ethernet cable. When the internet goes out the US/DS light blinks and the online light is off, however if I leave it alone for long enough the lights when go solid but the internet still doesn’t work. I’m hoping I need a new router/modem but it’s very hard to figure out how to get a technician out to replace it so I’m posting here.