Will coiling a mains power electrical cord cause interference?
The coils, if "air-cored", meaning that no metal passes though the center of the coils, should be relatively benign. Especially if both wires are routed together in the coil. However, if they are routed separately, and have any metal though the centers, then they will behave at least slightly as inductors and/or transformers, and three things may happen. 1. They metal or coils may get warm. 2. They may reduce the amount of power reaching the lamp. 3. They may audibly "hum" with the mains frequency. Any metal passing through them may also generate a current (transformer action) which may be negligible, or rather significant depending on the exact design. A picture here would be worth a thousand words.