I dont know which processor you have but it sounds like a mobile processor with Intel SpeedStep® or similar technology. To top this off it sounds like you have turbo boost on the processor which will clock the speed of the processor up based on temperature and the number of cores being used. Basically what it is does is when you are not doing anything the computer will step down to the performance to preset level to save power. This is on all of our processors so yes it is performaning right. So if you want some additional information you will need to provide us with the processor model.
It may be a power saving feature, if not a laptop then there should be away to disable in bios, or if a laptop the same, just many laptops have locked bios, but yes most likely normal, a more details on your setup would be alot more help for future posts