Inspiron 7737 doesnt wake up after sleeping mode. help please!

HI all! I recently bought this laptop and it was awesome until I updated to windows 8.1

It doesnt seems to be a very bad problem but it causes that the laptop is not working properly and is annoying. Apart from that it feels much slower under windows 8.1.

The problem comes everytime I leave the laptop alone and it disconnects the screen (because of the power plan), and when I try to continue working again the laptop doesnt seems to respond. The screen never switch on again, it doesnt do anything with mouse, keyboard, touchpad, touchscreen. You can hear that the laptop is ON, but there is no LED blining, the key for illuminating the keyboard works perfect, but it doesnt respond. 

Then the only thing remaining is to switch off from the button during 5 seconds and then it shuts down. But then the other problems come. The boot is veeery slow now, and when you are on windows you notice that there is no wired-LAN adaptor on the computer, then you want to stop working you use "shut down"... it will never shut down totally. The laptop will be forever "shuting down", with the ventilator at 100% until you decide to switch it off with the button again. (my longest test was more than 1 hour at it continued with out switching off). Then when you switch on again it will be still veeeeery slow and then the same problem shuting down. Until you decide to use the "Reboot" button. I dont know why but after this problem you do a reboot and then it works again normally shuting down and booting, and with wired-lan again!

Substitute character removed as per TOU>, this is annoying :(