I'm not sure why the system is coming out of stanby mode, perhaps some application is kicking it out, or the keys are being pressed somehow....maybe someone else can answer this.

 

However, it sounds like you carry your system around in its carrying case when in standby mode. This is a big no no! You should either turn off the computer or put it into hibernation. Even in standby mode, the system still running and generates heat so it needs ventilation...there is no ventilation in the carrying case.