Check your Settings. More than likely, you are receiving something (Mail,iMessage, game request, etc) that is activating your notifications. The iPad will come out of sleep to tell you of these notifications. Oh, and this is normal behavior.
The only was to prevent it is to turn off all your notifications or have the iPad fully off (using the "slide to power off") and not plugged in.
Marilyn
P.S. I've mergedyours identical threads of yours that you had posted in different places. Please, only post once per topic/question!issue. More than one fragments the conversation and makes it hard to follow. And, it's against our rules. Please keep any follow-up on this issue to this thread. Thanks for your understanding.