Do you have air bubbles entering the pool from your pool jets ?
Air is entering the pressure side of the system (between the pool to the pump basket).
Air is probably getting in either at the pump basket, or a PVC joint flowing into it. Hopefully, it is
close to the pump.
If your can see air bubbles in the pump basket, check the following until they
Switch off motor, check the pump basket lid is screwed hand tight
Check the basket 'O' ring for wear. add grease, re-tighten, look to replace the 'O' ring.
Some pumps have drain valves in the side - check for tightness/wear.
Run a water hose over the pump lid and PVC joints flowing to the pump - see if water is sucked into the system
instead of air. This will help narrow down the problem. Repair where necessary.
Following the above steps should isolate and resolve 95% of air bubble problems.