Transmission problem?

About a month ago when I put the car in gear (reverse or drive) the whole car vibrates until I take my foot off the brake and accelerate. When in neutral or park it runs fine and only does this when stopped in gear. Also once the car warms up it usually goes away and only happens occasionally while driving after warm up. Also even when cold it shifts normally. And yes it has the correct amount of fluid. Could this be a trans problem?