I Zone Out A Lot

Apparently it is my worst flaw and 9 out of 10 times I don't even realise I am doing it. I just switch off. I can be in the middle of a sentence or in the process of doing something. People have (in the past) stressed at me to snap me back into reality - I understand it must be infuriating but I can't help it.

It usually happens when I am tired and it is slightly irritating for all (including me) as I never know when I am doing it and I don't want to come across as rude - because I'm not but I guess it does have its advantages.