If, after feeding and at room temperature, your starter is doubling after something like 4 hours - you are fine.
The smell is alcohol - which is a normal part of the fermentation. The longer it goes, the more the alcohol accumulates. The shorter it goes, the less alcohol.
If your starter is rocking and doubling as described, then it is going past its prime at 12 hours and that is the alcohol smell. You can feed twice as often or, more likely, put it in the fridge until you need to use it. When you are ready to use it, feed it a couple of times until it is doubling nicely and you are ready to go.