The Agile Practice Guide, 2017, Pg 30, provides guidance on the agile transition strategy. It recommends using a hybrid development approach as a strategy to transition to agile starting with a less risky project with a medium to low uncertainty, and gradually trying more complex projects that require more of those techniques to be added.
Shu Ha Ri is a popular agile adoption pattern for teams new to agile.
Also refer to the brief case study under PMI’s Standard+ (free for PMI members):
Case Study: A Slow and Steady Introduction to Agile Through Hybrid