Engine Stalls

What is your question?

I am driving a automatic transmission. I reasonately discover twhen I start the car init idles, but the moment that I select R or D it has the tendency of struggling to move as if the brake is holding it back,and there after it stalls. When i restart the engine in either N or P it idles, and when I shift the lever to either 3 or 4 it still keeps the momentum, but the moment i select D or R it stalls. Can you please tell me what the problem is?