It could be several things, your recipe, your oven temp., or how you let it rest/cool once out of the oven.
I always have excellent results letting my cakes rest in the pan for exactly 10 minutes, level the top, turn it out onto serving platter, then let rest another 10 minutes, then wrap with Reynolds Plastic Wrap and let cool to room temp. I tend to bake my cakes the day before decorating, so this process works very well for me. The cake remains moist and has rested/settled and is ready for torting/icing the next day. It also helps that I am not tired or stressed for time, I get to relax and enjoy the decorating part, which is my favorite part anyway.
Why Reynolds Wrap? It is the ONE plastic wrap that always adheres right to the cake without a lot of fuss. Give it a try and see if it works for you.