The answer to 'why is my dimmer switch burning smell' is that a burning smell from a dimmer switch is typically a sign of an electrical issue that requires prompt attention. This could be caused by an overloaded circuit, a faulty switch, or wiring problems. The burning smell indicates that the dimmer switch is overheating and could potentially start a fire if left unchecked.
Some common symptoms of a problematic dimmer switch include flickering lights, intermittent operation, and a noticeably warm or hot switch. If you notice any of these issues along with a burning smell, it's best to shut off power to the switch immediately and call a licensed electrician to diagnose and repair the problem. Attempting to troubleshoot or replace the switch yourself could be dangerous if you're not experienced with electrical work.