If you're using baking soda + an acid as your leavening, then your rise can be inhibited if you wait too long to get the batter into the oven, of if you overmix a little.
Flour type also matters but the effects are non-obvious.
Science-y stuff: baking soda + an acid start reacting as soon as you put them together, making gas. If you overstir the batter you can knock the gas out, if you wait to put it in the oven the reaction can run its course and deflate before you set it in the oven. Double acting baking powder on the other hand has both baking soda and an acid combined already, and they don't start reacting till they get hot - so they don't start rising till you stick them in the oven.
Cake flour has less protein so it's more tender a cake, but also less strong. That can mean that your cake is delicate, and collapses (making it dense) OR that it gets a big rise because it takes less air to make it bubble up huge (because cake flour is physically less heavy).
The trick with a rise is to time it so that the cake remains soft long enough for the gas and water inside to expand and make bubbles, and then to have the protein structure set before those bubbles collapse. If the rise happens before the cake can set, it will be flat - like if the temp is too low, or the leavening happened in the bowl instead of in the oven, or if the batter was too heavy for the amount of leavening, or too light and you got a blow out.. If the cake sets before the rise, it will also be flat - if the oven is too hot, or the amount of leavening was too small.
TL;DR: if it's a cake recipe you've used before, with ingredients and equipment you've used before, it's probably your oven running a little cold.