There are many reasons that people move. Families grow out of their houses. Kids who shared bedrooms when they were small eventually want their own rooms as teens. Retirees choose to downsize to free up some equity for travel or a second home. We can't always wait for the spring market to buy and sell.
Don't postpone a milestone in your life because you are afraid it's not the right season. Just hire good help. A professional and full time Realtor like me can help you make the most of any market.