That's not too bad really... But if anything were wrong(and causing such a problem) it'd be your powersupply or motherboard. If it were your CPU, the computer probably wouldn't work at all.
One more thing that I would question is the readings being true. Check in the BIOS for what that shows you. However, fluctuations always occur. I would also bet that if it indeeds fluctuates, it would, as mentioned above, most likely be the mobo or the PSU.