I have an RGB LED 8x8 matrix which is claimed to consist of WS2812. When turning it on, it automatically lights up all LEDs white with full brightness. The LEDs even light up without DIN being connected. I remember reading something about this behaviour and I think it was related to the LEDs being SK6812 or similar rather than WS2812, but I can't find this page anymore, nor anything else describing this behaviour.
My question is, how can I disable the LEDs lighting up when turning power on? Of course I could add some kind of relay to switch them on right before the signal is sent by the Arduino, but is there something simpler?