Possible Solution?
I think I have found the solution for this nasty problem.
I've tried everything I have read here in this thread, factory reset, enable/disable apps etc. etc. I've called Samsung in the Netherlands and strangely enough they had never heard of this problem. There advise was to take the phone to a service center and get a deep factory restore???
Based on the occurrences I got me thinking that it has something to do with the lock screen, and yes i've tried disabling and enabling the camera short cut but without any results. Than I have read something about the health apps, also enabled/disabled them.
Than I noticed that the lock screen displays the actual weather forecast on the lock screen, so i've disabled the additional information function.
This function displays the weather and the pedo meter from s-health...
Since disabling this function, no more black screen for me! I hope this help some other S5 users out there!
Settings>Lock Screen->>Additional Information to Off