I had a similar problem... black screen but had sound. Only on start up and only the past Couple days disconnecting and reconnecting the hdmi at both the tv and the ps4 worked initially, but on the 4th day of the issue, when I got the image back, it dropped out again after a few seconds. After that, disconnecting and reconnecting didn't bring back the image.
Luckily I had just gotten a new hdmi cable for a new 4k device, so I swapped to the new cable. No issues at all since. I think there are flaws with the OEM HDMI cables.
