2013 Ford Fusion: Radio & Heater/Defroster turn on and off by themselves

The common thread here is that all of these items are electric – so it sounds like you are intermittently loosing electrical power. I'd suggest starting off by getting codes read, it's possible that a controller will be logging power loss events and that there may be some clues in that.

Since the power goes off and then comes back on there are three explanations that seem obvious:

1. A load reduction relay dropping out or a self-resetting circuit breaker is tripping and then after a bit resetting.

2. A connection is loose and is opening up in response to vibration (or something).

3. A large intermittent load (or short) is pulling down the electrical bus (making it seem like power is being lost).

The items that you're seeing don't have much in common. I can almost guarantee you that they are not on the same circuit, so you'll want to look for common points upstream of the fuse panel. That makes the load reduction relay seem like a possible candidate. Another clue that the load reduction relay might be worth investigating is that you don't notice the instrument panel going dead when this happens. The instrument panel is probably not fed through the load reduction relay. The connections at the main fuses (usually near the battery) might be another possibility.