Windows 8.1 100 disk usage on my computer

My computer is running at 100% disk usage and it happens randomly. AVG usually appears on top of the list of the disk read/write. All the drivers installed on my computer were properly installed and working properly. Just today, just right after startup, the same thing happens and it seems that my computer is busy doing a lot of things and as a result, my PC froze for few seconds. The mouse pointer was also not moving and after few seconds, it unfroze itself. I am bothered with what is happening and I don't know how to fix this issue. So I am asking the experts here for some suggestions on resolving it.
