So I was up an flying around 9AM today when, as I leveled off at 3500 feet, Foreflight called out a traffic warning. My altitude, less than .25 miles at 9 o'clock. No traffic had been seen visually on the climb and visibility was good enough. Scanned the sky and saw nothing. About 2 minutes later, another warning same altitude, <.25 miles 1 o'clock. Scan, clearing turns... nothing. Finally called up a nearby class D tower to have them see a) if there is anything on radar near me and b) if they can confirm my ADS-B tail number (thinking I was getting an echo of my own plane so maybe I was not transmitting my tail number (?) ) Tower confirmed my area clear and had me call atlanta approach for ADS-B confirmation. They confirmed tail number transmitting correctly. There was a little pucker factor due to the warning but I mostly want it fixed so that false positives don't cause me to not take the traffic warning as background noise. ANybody ever run into anything similar?