MacBook Pro (mid 2012) turns on when lid is closed and MagSafe gets attached or detached.

Question

I own a mid-2012 Macbook Pro with the 15" high resolution screen add-on (it's the model that was released alongside the new retina versions). The processor is a 2.6 GHz Intel Core i7. I run OS X 10.8.4.
I'd like to know if the following behavior is normal: when the computer is sleeping with the lid closed, and the MagSafe adaptor is either attached or detached, removing it or attaching it (with the lid still closed) will make the computer wake up from sleep. You can easily hear the fans starting when it does so. It'll stay on for 30 seconds to a minute, and then go back to sleep again. The screen doesn't seem to turn on when this happens and the lid is closed. Opening the lid when the computer exhibits this behavior results in a black (and useless) screen. In order to be able to use the pc you need to wait until it goes back to sleep on its own and then turn it back on. 
Another (possibly related) issue appears when the PC turns off automatically (either while running or during sleep) because the battery is exhausted. When this happens, I usually attach the adapter (with the lid open, most of the times) and then press on the power button. A black-and-white screen with a loading bar appears for a few seconds, and then the full-color login screen appears (my pc is set to ask for the password every time it wakes from sleep). After the loading bar is gone and the full-color screen is back, I am unable to input my password, even though the password field looks focused. Neither the keyboard nor the mouse are responsive. This often happens in such a way that it is impossible for me to input my password (or interact with my pc) before it goes back to sleep for lack of interaction. Recently I've discovered that randomly pressing the power button and some keys on the keyboard (I still don't know what exactly triggers this) will make it able to receive input and thus I'll be able to type in my password and log in. 
I'd like to know if any of you have encountered the two behaviors I've described and if you think they're normal or have any solutions for them.

Answer 1

Hello terabytest,
I would be concerned too if my MacBook Pro exhibiting the behavior you described.  For a message like this, I recommend resetting your System Management Controller (SMC) and NVRAM.
Resetting the SMC on portables with a battery you should not remove on your own
Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).
Shut down the computer.
Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
Release all the keys and the power button at the same time.
Press the power button to turn on the computer. 
Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.
You can find the full article here:Intel-based Macs: Resetting the System Management Controller (SMC)http://support.apple.com/kb/ht3964
Resetting NVRAM / PRAM
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
Turn on the computer.
Press and hold the Command-Option-P-R keys before the gray screen appears.
Hold the keys down until the computer restarts and you hear the startup sound for the second time.
Release the keys.
You can find the full article here:
About NVRAM and PRAM
http://support.apple.com/kb/ht1379
Thank you for using Apple Support Communities.
Best,
Sheila M.