Hi Tired Momma!
The diagnostic guidelines for ADHD were changed in 2015 to lower the age of possible diagnosis to 4. It is certainly possible to see it early in kids who have more severe ADHD.
That said, the behavior you describe could signal other things — on their own without ADHD, or in addition to ADHD. Anxiety, autism, and SPD call crossed my mind as I read your post. That being the case, a more thorough evaluation should be done, not just looking for ADHD.
The best thing you can do right now is to consult a psychologist or psychiatrist and discuss what’s happening and next steps. They may advise evaluation now, or they may suggest counseling and behavior modification now and waiting until he’s 4 for evaluation. The earlier intervention begins, the better the long-term outcome though, so keep that in mind.
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism