I get them too. Seems to be a troublesome spirit. Try some cleansing and protective shields around yourself or your area.
A lot of people like to assume demons for anything involving to painful scratches to possessions. I personally think it could be anyhing causing the scratches. Even the most "divine/holy" creatures can do acts such as these.
Also, just an advice, the more you ignore the less they bother. And don't tense or freak out about it. They tend to feed off the reaction. Stay safe.