It is, I'm fairly sure stutters can be developed at any time. The later in life it pops up, the harder it is to remove. I myself developed a stutter in my teens. My family and I cannot remember the exact time, or situation (no trauma either) - but we think I was probably 12-14. My best guess would be the stresses of high school. It's fairly mild compared to others and is mostly compromised of blocking. Have you looked into speech therapy?