Does excessive amount of air at the pump suction cause cavitation?

Answer: No. Air has nothing to do with it. Cavitation is caused by the collapsing (imploding) vapor (not air) bubbles. These bubbles are simply a vaporized liquid in the region where static pressure dropped below vapor pressure. Air causes other problems, such as air locking, and even a very small amount of it causes significant loss of performance (head drops), but this is a different subject.