Sounds like a case of
Water Hammer .. While water hammer can be a variety of reasons .The 2 most common for sprinkler systems are 1) High Water pressure and 2) The water velocity in the pipes are traveling too fast and above the code of 5/7 FPS
Find a way to get an accurate water pressure reading
If the pressure is higher then 80 PSI I recommend a
Water Pressure Reducing Valve