Yosemite Frequent spinning pizza ball

Often when changing within an application what I'm doing( going from making entries in quick book) to say, looking in the cart of accounts for a different account I get the spining ball for maybe a minute and then I' able to proceed. Same may happen if I swich to the finder from an app. To launch another program. THe ball spins and after a minute I can work again until I try something like saving a file. I hang for another minute. Swich to an open word document and clicking on something to edit and I hang for another minute. I have a fast i7, 8 Gb dram, so I doubt it's resources. Activity monitor may often show the app. As non- responding until my minute is up, then thins are all backgrounds to normal. I,be only had this problem in Yosemite. This suggest anything based on our experience.