for well over a year my router has a mind of its own and will turn itself on and off. I called Virgin Media and they told me to take out the Ethernet cable and use Wi-Fi, which I did and it hasn't made any difference.
It is most likely to turn itself off when I turn on my PC, I have to use the troubleshooting guides and not even that can get me back online.
Can you post your Upstream and Downstream dats please so that we can see if there's a power level issue. Type 192.168.0.1 into your browser's URL which should get you into the Hub's management screens ... do NOT sign in, just click on Router Status where you'll find the data pages.