dell laptop restarts after displaying dell logo

[Prap82]

Hello guys..
I am using dell vostro 3400 laptop. All of sudden it is troubling me like when I switch on - it loads up to dell logo and a blank scree appears wit a cursor. Then it automatically restarts and same process repeats...
I ran system diagnostics but there was no error message. I tried to enter safe mode by pressing F8but it didnt work...pls suggest what to do....

 

[jsmithepa]

Consult manual and attempt to: (1)RESET CMOS, (2)RESET TO FACTORY.