Pixelated tv

We have been experiencing random pixelated tv screen on three different television sets on live or recordings of live shows. We have checked several networks, and all are pixelating—sometimes so much that it can’t be watched. It comes and goes with no apparent reason. I have checked cables and rebooted our Gateway with no improvement. I think something is wrong with the cable coming into our house. My address is [Edited: "Personal Information"]. Telephone: [Edited: "Personal Information"]. 
Please advise a fix.  Thanks, Grace [Edited: "Personal Information"]