Sobriety.
I quit drinking again last week. I was sober for over four years. I had begun to goof with my sleep routine (which has not been "routine" since my wife started to work third shift, last fall), thinking that some alcohol at various times during the day might help. It didn't help. In fact I got less sleep than before, but I messed up by changing too many things at once. I'm not sure what went wrong. It helped in the past ...
Plan B is to get totally clean again and try to change only one thing at a time, until I find the silver bullet to kill random wakefulness once and for all. I should be taking my morning nap, right about now.