Weird power on issue

I have a XPS 15 9560 laptop with a strange power issue.  I think it may have started after updating the BIOS but I've tried additional updates and it's still there.

It works normally whilst using it but when I put it into sleep mode or hibernate and then come to turn it on again, it hangs on the Dell screen.  There's no timer or anything, just the static Dell logo and a black screen.

This happens whether it's after an hour or a day.  The only way to fix this is to hold down the power button and do a hard restart.  This obviously wipes all the open programme data so it sends Word etc. into document recovery mode.

It's a right pain and I've searched Google for hours looking for a solution, but haven't been able to find this exact issue.  Can anyone help?  the laptop is a year out of warranty and I'll be very annoyed if it's broken!