I have a Sony KDL46XBR4 LCD that has a problem

You are getting the issue on a cold start which means the LCD Panel is bad. It is usually the inverters that cause the issue. They are what light up the panel. This problem was present in many of Sony's LCDs released around the same time as yours.

You can check the voltages to see if the inverter boards are functioning correctly. If Inverters should be replaced. Part numbers:
Inverter Left: 1-789-839-11
Inverter Right: 1-789-840-11

If the voltages are fine or the Inverters did not fix the issue, you need to replace the whole LCD panel which is very expensive. The part number depends on the serial number of your TV.

1-802-491-12 for
S/N 8,000,001 TO 8,199,199 AND 8,500,001 TO 8,599,999S/N

1-802-491-31 for
8,200,001 TO 8,499,999 AND 8,600,001 AND UP

The inverters list for $93.11 each while the LCD Panel lists for $1400 with a $3100 core charge.