You may not have a problem -- if the sump is small (say about 12" diameter) then the pump is removing water faster than it can flow in and quickly empties and shuts off, just like it is supposed to. Since the sump is small, it quickly re-fills and the pump turns on. While this is not the best of all possible situations it seems to be working. You might do a little digging on the outside of the sump and see if the rock around the sump has become partially plugged with soil, if so then dig out the rock and replace with clean rock. This will improve the flow into the sump and allow water to enter faster so the pump doesn't cycle so frequently.