Edit: I have root without tripping knox and applied the posted settings for setcpu and it's been a day no reboots. Going strong. Can't thx enough. I usually have 4 5 freezes and random reboots every day but nothing so far
Update : hello everyone this is for the people who do not want to root their phones. Long story short I wanted to unroot the phone for Warrenty purposes. So I flashes the rom with Odin. The restart came back. However I decided to refresh my phone using kies 3.0 and guess what I was able to flash firmware through kies and the problem solved. No freezes reboots. No root required. Mind that I flashed different version of my carrier's stock firmware though Odin but the reboot problem persisted. But after flashing through kies. It's gone. I am a happy camper again. Good luck to those who don't want to root their phones. Gives kies 3 a try and see if you get rid of random reboots.