Hi Cedar,
What you are describing is an aura sz. Often I will be sitting in my living room and all of the sudden start to smell natural gas or a burnt odor. This is a form of a aura sz. and just like you I feel no sz. starting. Aura sz. are also known as simple partial sz. The reason why you might have gotten this is because you have been sick with a cold or sinus problems. Every time when I'm sick with a cold I always end up having some type of sz. Here's wishing you well and May God Bless You!

Sue