A.Z.
If he is completely unresponsive during these episodes, I would keep pursuing this. Unfortunately, to get a better diagnosis your will have to be older and be better able to communicate if he is having sudden dizzy spells, nausea, head pain, memory loss, etc.
It could be a migraine which would result in normal EEG and MRI, and the only visible symptom is stopping and staring into space. It could be autism, or a long list of other things.
Right now, there isn't much that can be done unfortunately. As much as you would like an answer right away, you might just have to wait and keep a log of when he has the episode, how long it lasts, what he eats daily, what activities he does throughout the day, how much sleep, how much he eats, his moods for the day, if he shies away from touch, and the activity he was engaged in when he gets the episode.
The doctor can run some tests but the best way to get a faster more accurate diagnosis is a very detailed daily log. It can identify patterns which might not be readily seen.
That is not to say you shouldn't keep at it. The behavior isn't normal. He needs more tests but detailed log will go a long way in speeding up getting him diagnosed.