Yes you will start a cycle, how much sand you add with determine the size of the cycle you go through. Personally I would add the sand in small amounts over a month period, to reduce this effect as much as possible.
Of course I am that this is a cycled active tank and you have livestock in it.
Also if you are moving you should either add the sand and let it cycle, putting your livestock somewhere else until it cycles or put your livestock back in and then wait about a month to start adding the sand. The move could potentially be very stressful to the livestock adding sand at that time would most likely add to the stress factor.