I had this problem a long time ago, the computer expercts said that the HDD is 'dead' so I replaced it, it worked fine. Now in last few days/weeks I've noticed that my PC restarts itself again without any warning. It's not so annoyig yet becasue it doesn't happen everyday and usually afer computer starts not when I use it (well sometimes it does, but rarely). Event viewer says it's Kernel-Power, the same problem as I had a year ago or something like that. Firstly I would like to know how can i check if everything is OK with software, I runned windows defender but it didn't find anything. I have genuine Windows 10 Home. Thanks everyone for help and sorry for my english.
Event viewer picture: http://prntscr.com/d5yokt