Al PB 17" - Would not Restart- Strange Behavior

[Seymour J. Wolfson]

This morning I closed the cover of my Al PB 17" while it was running, 
and took it to another room.  There I opened it and it would not come 
back on no matter what I did. Just had a black screen. I tried 
hitting some keys, pressed the power button, held down the power 
button for a while, but nothing would get the Mac to turn on.
  About an hour later, I tried to turn it on again by pressing the 
power button and it started just fine.  This is a real mystery to me.
Is there any reason for any of this and what is going on?
-- 

Seymour