No signal detected

When I turn on my TV, I'm met with the Xfinity welcome screeen, where it says "Welcome. Bienvenudos...".  But after a minute or two, the screen goes to a picturesque screen saver-type image, and a small gray text box comes up over that and says I have no signal, and suggests that I check all of the physical connections.  The connections are all in place, so I don't think that's the issue.  Regardless, I unplugged the power from the xfinity box a reconnected it after a minute, and after a few minutes, it worked again.  But then the next day, it stopped working again, and every time I go to try and access my xfinity tv channels, I get the same process of the "Welcome" screen and then the "no signal" screen-saver image screen.  It might be worth mentioning that this is only the case for the TV in my living room.  My bedroom tv (which has its own separate xfinity box, has no issues at all.  So what's the solution?