My hp pavilion dv2000 running

Question

my hp pavilion dv2000 running vista home prem will suddenly restart itself for no reason.sometimes when i'm at the computer just surfing and others when i'm not even at it.happens every couple of weeks. my computer is generally pluged into a network so i don't know it's a remote command but i haven't seen anything pop up. also i have my firewall blocking most things i think.regards