An article by Lindsey Wegner, M.A., CCC-SLP

When should my child start speech therapy? This is a common
question for parents who are wondering if their child is in
need of speech therapy services. The answer is… it is never
too early. If you suspect your child may have a speech disorder,
it is important to receive an evaluation as soon as possible.
The more help your child receives early on, the more likely he or she will benefit from
therapy.

https://www.superduperinc.com/handouts/pdf/500_tisNeverTooEarly.pdf