My system freezes completely at random, frequent intervals. I started to have the same problem in Ubuntu 14.04 but after recent upgrade to 16.04 there is no improvement, in fact it seems worse.
When it happens, it's impossible to do anything. I've tried everything in this thread: What to do when Ubuntu freezes but nothing works, I have to hard reset. I have read all the system logs and
journalctl but there is never any information that could help diagnose the problem.
This is a dual-boot system with Windows 10 and there's no problem there, so it's not defective hardware.
My laptop has an Intel Bay Trail processor (Pentium N3540)