Laptop Fails to Restat after loging off

Hello,
good afternoon

Got an accer aspaire laptop, aweek ago it put on and tried to resart but it was in vain, the power goes in, it nruns the fun for few seconds it stops and then runs th DVD ROM for few seconds and then back to the fun permately and no display on the screen.

But after like 7 hours the computer when i press the retart button it does it responds and i can domy work but when i attempt to restart it shuts down but it canot resart

What could be the problem and what shoud i do ?

Thanks
Evans Uganda