You should try an official walkthrough with MS support to see if you can get a better diagnosis. Typically tech support issues on forums are missing several steps with unclear information. Try giving them a direct call. That's what they're there for.
I restored my device before seeing you post. I called MS support anyway. He had me lengthen the time of sleep and display off in power options. He said hitting the power button really just turns the screen off and doesn't go to sleep until the time in power options. Additionally, he said the issue may not be the tablet not waking up, but the screen not coming on. He said there may be something running in the background that's preventing the screen from turning on. I'm not really sure how lengthening to two times does anything and doesn't really explain why the tablet will come to the Surface screen after ten seconds instead of the lock screen if I only have the display off for a couple minutes.
But, since I just restored my device, I don't know if these settings will actually help or if it is in fact a program I have installed. Will update once I have things installed again.