As Wamasa said, you could use setLooping for infinite playing.
For playing only a specific count time, you can add an onCompletionListener to your MediaPlayer:
int count = 0; // initialise outside listener to prevent looping
mediaPlayer.setOnCompletionListener(new OnCompletionListener(){
int maxCount = 3;
@Override
public void onCompletion(MediaPlayer mediaPlayer) {
if(count < maxCount) {
count++;
mediaPlayer.seekTo(0);
mediaPlayer.start();
}
}});