What is the ruling on selling a car that was purchased with the intention of selling it when its price increased, then the intention changed to keeping it despite its price increase, then it was later sold at a low price not with the intention of profit?

There is no zakat (definition) due on you for the car's price, unless a full year passes while it is in your possession; because your intention changed from trade to personal use. The intention transfers to personal use what was intended for trade, but it does not transfer to trade what was intended for personal use. If you intend to trade with it again, its intention does not transfer to trade merely by intention, according to the well-known opinion, and it becomes like goods for personal use.