Over the last few days my oil burner has been acting up. First, it would run normally, but while it was running the flame would go out. Then it'd come right back on. It only seems to do this when it's hot, when it first starts up it runs fine until the temp gets up around 180 or so. Yesterday I replaced the oil filter (on the line that comes from the oil tank), bled the whole thing and got it fired up again. Overnight, the burner shut down and this morning it was around 50 degrees in the house. I went down to check the burner, it was off and the temp was low. I hit the reset button and it fired right up, heated the house up. But after it while it shut down and didn't automatically restart even though the temp was lower than the thermostat settings. So today I changed the nozzle and the the filter on the motor. It's still doing the same thing... once it heats up the flame goes out then comes right back on. And once it's warmed up, it shuts down and then doesn't automatically restart Any ideas about what else to check?