Problem with CM600 Modem, have to disconnect every time

Just moved and bought CM600 modem to use in combination with an HP Envy with Windows 10 and Comcast Xfinity service. Cable guy set up and everything went ok for the first two times connecting to the internet. But now every time I boot up the internet connection is slow and then stops completely. Using Command Prompt upon start up, pinging a site fails and I get timed out at either the first or second step when tracing the route, suggesting the problem is on my end.

 

Unplugging the modem for 1 min allows me to establish a connection, but  simply disconnecting the cable from the computer or the modem for 1min will also clear up the problem.

 

One person at work says the modem is bad and one says its a software problem. Any suggestions or anybody else had the same problem? Unfortunately I leased my last modem from Cox so this is first one for me to own, don't have a back up to try and replace the current one.

 

Thanks for any help