Can you think what to think?

I was wondering today what if you had to think something to think about.... I mean everytime we think, its about SOMETHING, so what if you had to think about something to think about.... Dunno what I am thinking but I AM :)..
Sometimes mind just goes blank with nothing to think about, what do anyone do then! I don't really know what I do at that time, cause I don't really remember of it. I believe that's when I am really thinking about something to think about, and its totally weird. If you understand what I am writing here, please put your thoughts here. I will need em next time I get into the thinking to think business.