Dell Inspiron 7537 doesn't start after closing a lid

Hello,
I recently bought Dell Inspiron 7537 with Windows 8 (which I updated on 8.1).
When I close a lid and after some short period I re-open it, my laptop starts up normally (let me to log-in). However, when I close my lid and leave it like this for longer period of time (typically when I leave for work), then the laptop doesn't start - after reopening, the keyboard light is on but computer doesn't start. In addition, there is no respond even  when I click on the power button. I have to push the power button for a while which consequently shuts down the computer (keyboard light turns off).
Do you have any tip how I might solve it?
Thank you.