Trouble with Dell Inspiron 15r 5537

Hai all, 

        I recently purchased a Dell Inspiron 15r 5537(i5-4200,8 gb ram, 2 gb Radeon 8670m ddr5, 1 tb HDD) and i've had numerous problems with the same. Any suggestions are welcome. Thanks in advance. :emotion-2:

First of all, the pc takes like 25 seconds or so to boot up. After the DELL emblem, I get a blank screen for like 10 seconds (Sometimes a "Please Wait..." msg appears.) Even after I enter the pin, there is a lag of 2-3 seconds before the "Welcome" note appears. The lag continues even after booting (windows and programs are slow in loading). I tried disabling Startup programs and updated video drivers with no result.

Secondly, every time the pc goes to sleep, it doesnt resume normally. The power and wifi lights are turned on but the screen remains blank. If i turn off wireless, the light goes off so the computer must be ON but without display. And then i have to do a hard boot.

Any suggestions ??? Thanks in advance.