Welcome to Android Central! Stray electromagnetic fields can cause ghost touches, so make sure the phone isn't near any strong sources (like a big stereo speaker, or a computer's power supply). Does this happen only while charging? Some devices may have poor or faulty shielding of the charging circuits, which could potentially cause problems.
How new or old is the phone? Any recent trauma or water exposure? It may just be a faulty digitizer that needs to be replaced.