Im cant say for the specifics of a 2004, but on my 2014 this is part of the memory settings. You move the mirror to where you want it while the car is in reverse and then store it using one of the memory buttons. You then have to check a box within the reversing settings on the console to activate it to happen automatically.
If the same as my car, you should be able to find this option using the stalk and then disable it. You can still make it happen manually if needed by simply pressing the corresponding mirror button when in reverse if the auto feature is disabled, or you can completely remove the possibility of it moving under any circumstance by storing it to memory again in the driving position while in reverse
Thanx unfortunately the 04 ha no dash of indicators all I have is 4 buttons 1-2-key-m
When trying to position mirror while in revers key on it won’t stay there rather keeps going into unwanted position