My 3yo started stuttering

My 3yo started stuttering Hello. My 3yo boy started stuttering 10 days ago, and it became really bad real fast. Yesterday he would stutter on every phrase, he does repeat words more than sounds or syllables. Even though he doesn't seem impaired by this sometimes when he is repeating he speaks in a lower tone of voice, so I believe he is aware. We have taken him to a speech pathologist, she did an evaluation and said she wanted to check on him after we return (as we will be staying away for the next couple of months). Does this happen to anyone of you? Is this a come and go thing?