From the 'Helpful Tips' pages in the Home Service section of my web site:
If you have to transport the fridge you can lay it on its side. It's best if the hinges are at the top so the doors don't fall open. After moving, you should leave it stand upright at least an hour before plugging it in. This is because when horizontal, the oil in the compressor will seep into the refrigerant lines plugging them. The idea is to give it time to let it settle back into the compressor harmlessly. However, the less time it's on its side the better.
It is also a good idea to minimize shocks to the appliance when horizontal as the compressor's internal suspension is not engaged in that position and they may become dislodged if jarred too much.