Why does my Check Tire light come on sporadically even with new tires

Why does my Check Tire light come on sporadically even with new tires I have a Ford Freestar 2005 and the “check tires” light comes on sporadically for no reason. When I check the pressure in all tires it is normal. I just got brand new tires 3 weeks ago and the “check tires” light has come on 3 times already!!!!