The focus/popping problem began happening with my monitor a couple of months ago.
After it started, it would take a few minutes for the focus to stabilize with the "pop". It gradually took longer for the monitor to pop.
A few weeks ago, the monitor wouldn't pop at all after hours of waiting. I had to shut it off and on a few times to get it back in focus. The focus problem would mostly appear at alternating power-ons (every other day).
Finally, I decided to just let it stay unfocused, and left the monitor on 24/7 with a blank screensaver. According to previous comments I had read, the problem was caused by a short in the tube, and leaving the monitor on for days or a week could possibly burn through the short.
Afterwards, I noticed that the picture was appearing a lot less blurry during the times it was out of focus. I continued to leave the monitor on for a day or two whenever it started up unfocused, with the contrast at 0 and brightness at 100 or 0.
Within the past 2 weeks, the problem has not re-appeared. The monitor has started up in focus every time. Maybe there's some life in it yet.