Depending on the sump pump's type; submersible (with magnetic, packed or mechanical seal) or pedestal (with motor above the water line). For as long as pedestal it completely dry and no water remains in pump's impeller chambers there should be no problem at all. Submersible / magnetic with completely sealed motor and impeller driven magnetically – there should be no problem with cold storage if fully dry.
Submersible sump pumps with packed or mechanical seals might not withstand freezing temperatures well. Depending on the seal and its design there’s always a chance that some water or even moisture will remain trapped along the shaft. When freezing and expanding it could break the seal and result in internal leakage when the pump is used again.