Well, it's either hardware or software.
First try the software. Read how to restore the laptop to factory conditions in your user manual and do that. If it's OK now it was a software issue (malware, or a bad update or a very bad setting you did yourself).
If it doesn't help, it's the hardware. After "several months" you stilll have warranty, so they will repair the laptop for free. Be prepared you'll have to miss it for a few weeks at least.
everybody.. i just bougth my new notebook and choose os windows 7. After several months my os (windows 7 home premium) got the trouble. The trouble was always restart it self, and i dont know what cause it..
so heere i wanna ask every body to solve my problems above.