Don’t know if this will help, and have no idea what’s causing this, but it sounds like a situation that is disruptive to good sleep. Could you be retaining water in your lower extremities (gravity) during the day, and then, when you lie down, you are suddenly processing it? Maybe if you put your feet up at least as high as your heart for an hour or two before bed? Read/watch TV, etc in bed, before you go to sleep? Best wishes.