How to ignore an undesired short output signal coming from arduino?
Use an invert circuit to create an active HIGH signal.
Connect the GPIO to an npn transistor base. Connect the collector with a pull up to the relay board and the emitter to ground. 
When the pin is low (like at startup) the relay input is high (from the pullup). If you switch the GPIO HIGH, the npn becomes conductive and pulls the relay input low.  







simulate this circuit &ndash; Schematic created using CircuitLab