It has only happened to me once - a long time ago. I was in the kitchen preparing the evening meal, and at the same time sorting out the food for our three cats and one dog whilst being supervised by said hungry cats. Almost at the same time the dog, my children (then aged seven and four) and my husband entered the kitchen (he had only just arrived home from work). It was instant chaos with the dog wanting his food and the cats' food also, the children wanting something to eat and drink, my husband wanting a cup of tea, and everyone wanting it all at the same time! At that moment the image of Frown Strong's card the Magician came to mind - I could see it clearly in my mind's eye - and I hadn't used that deck for a long time! Frown Strong's version of the Magician shows a Juggler. From that moment on my interpretation of the Magician is now based on the idea of a Juggler, making or trying to make some sort of order out of apparent chaos and keeping things in motion otherwise they would all fall down.
This is the only occasion on which a tarot card has spontaneously come to my mind's eye, and actually I thought it was rather neat. Usually I am just reminded of a card when a situation occurs.