It sounds like it may be fuel related, it could be an injector sticking open, and then closing, it's hard to tell for sure, but it wont necassarilly set a code. I would recommend having the injectors professionally cleaned and then if problem persists, you may want to put it on a scanner to be able to watch live readings on the engine performance. This way you can watch the action of each injector, and see if one is falling out.
If you have further questions on this, please feel free to reply.
Thanks for asking!