Hello and welcome to justanswer.com. I am pleased to assist you. The swelling or edema that you describe as relieved by rest and elevation sounds to be that you may have poor valves in your veins. These veins have trouble pumping fluid back to your heart against gravity. If not cellulitis or an infectious cause, and unless you have been diagnosed with heart failure, this is the next likely possibilty. It does occur more in overweight individuals. If you are thin, this can still happen. There are ways to reduce this swelling. Elevation when resting is good but during the day when you are active you may want to wear compression stockings. Any varicose veins (superficial and blue) that may appear can be removed for more cosmetic appeal.
I hope this helps. Follow up questoins are welcome.