TV stations are required to offer a secondary language option for viewers in addition to the primary audio offering of English. Something is happening within your TV remote/TV set at home that has, for some unknown reason, switched your audio to the Spanish (secondary option) option.
If you're hearing the broadcast in another language, it's likely a setting on your TV was accidentally changed. Spanish audio is only offered on some programs, and when Spanish isn't offered, English audio is usually broadcast. That's why you may not notice the setting was changed until you turn on a certain program.