This discussion could be a little clearer. "Key fob" usually means an object separate from the key, that the key is attached to. My Tacoma had one. My 2016 Rubi has an "integral" fob that is part of the key. It sounds from the description like the security light comes on and off while driving. That light should only be on when parked and everything is off, and the vehicle locked. The description sounds like a electrical fault, or if the fob is actually integral to the key possibly a bad battery. A photograph of the key would help clear up possible confusion.