I've always viewed the Doctor's regenerations as being fairly trumatic experiences and somewhat atypical of most Time Lords. Living considerably less dangerous lives than the Doctor, I think most Time Lords regenerate only when their current incarnation is about to wear out (either to old age and/or disease) and some can actually prepare in advance when it's time to move on to the next one and even control what they're going to look like in their next life. His former companion Romana regenerated simply because she wanted a change.
In comparison, the Doctor's regenerations are generally unplanned ones and the new bodies he acquires are pot luck. As mentioned earlier, the Time Lords chose what he would look like in his third incarnation, though. But I think the Doctor had time to choose what he looked like in his eleventh incarnation, but not having much practice still wound up with something essentially random.
The Fifth Doctor (seeing himself in a mirror for the first time): "That's the trouble with regeneration. You quite never know what you're going to get."