The best way to check for suction conditions is with a vacuum gauge on the suction side of the pump. You want to install it where it won't be destroyed by overpressure when the pump goes off. The gauge either has to have a maximum pressure capability consistent with the pump shutoff or it has to be installed on the well side of the check valve.
Your shallow well pump is rated for a certain "lift". If it is more than 20 ft, the pump will have significantly reduced flow and pressure capacity, and 25 ft is the maximum rating for most pumps.
You can get a vacuum-pressure gauge that has a range from vacuum to 30 psi from Grainger, Stock No. 2C515.