With the rise in temperature, biological activity in your pond is about to start up again. With the filter system not running, it is a great time to check all parts of the pond for damage or wear. Spring startup is also the best time to replace any damaged filter pads and UV clarifier bulbs.
Once the filter system is running again, you can start feeding fish sparingly in order not to overwhelm the pond with a high organic or nutrient load. It takes about six weeks of 55°F+ weather for the beneficial bacteria to resettle and for filters to be at working levels.