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After updating have you tried...
I have exact same problem. Since the update around March 1, phone constantly stays off, despite trying to turn it on. Doesn't matter if it's closed or open. Have to reboot it using power/volume down several times daily!
I also just applied latest updates April 19th.
I've tried the wipe cache, no change...same issue.
Samsung please fix this!!
"WIPE clear cache only possible if you have another smasung device to connect to"
You can connect it to a computer, also. See, video...
Ensure that you are using a Samsung data cable and not just a charging cable. Also, it can help if you have Samsung's Smart Switch installed on the computer, with its drivers.
If you have a black screen you will not be able to use Smart Switch.
Might be a good idea to take or send it to a Samsung Service centre.