I had power buttons on one set of monitors in the worst possible spot, so I would leave them on after turning off my computer and just let them sleep. I quickly found out that every 15 minutes or so the monitors would come out of sleep shining all the glorious light into my face as I was trying to sleep. I since fixed the issue by turning off the power at the outlet.
That also works too. I modified the chord on a problematic monitor to have a lamp chord switch on the cable. If I want the monitor to not turn itself on, I just flip the switch on the chord off and it can't turn itself on anymore. Worked well because it has a two prong chord same as lamps do.
I'm having this issue on my windows box so that won't be related. It's also happening when the machine is fully turned off so I wouldnt expect any drivers to be doing anything.
For some reason, if I turn my ceiling fan off, my monitor backlight turns on for a second before turning back off. It's fairly consistent, and I have no idea why.
Potentially a brownout on the circuit causing the monitor to turn on like its power has just been connected, before turning back off when it sees the computer sending the monitor sleep signal.
Pull the plug out, or if you're like me. Attach a lamp chord switch to the chord of the monitor and just turn it off that way. Can't turn itself on if it doesn't have any power.