is caused because of signal drop, this can happen at the location of the event being recorded, such as a live event. This can also happen because of snow on your dish, lots of tree blocking your dish ect... Solar flares can even interfere with tv reception even if you have cable, because most of the channels are being bounced off a satellite at some point & solar flares have damaged commutation satellites in the past.
If the image freezes for a few seconds on a live event or prerecorded event, it is part because of the camera/software used. If a signal drop happens the last image received will stay up untile the signal is re-established. You see this a lot if there using a helicopter for shots.