AT&T cordless phone screen lights up unexpectedly

Does anyone know why the caller ID screen & backlight of the cordless phone comes on even though no call is coming through? The phone is charged and sitting in its cradle. I’ve noticed it before and thought I was imagining things, but I’m not ... Will check and record the times to see if this happens at regular intervals. I noticed it sometime before 7:52 pm AST. Internet search led me to this website.