Have you tried to dry a prep and find water in with your air for the first few seconds? It can be frustrating and annoying. This is a problem most practitioners will encounter now and again but it can be easily remedied.
As long as the moisture in the air doesn't persist, you've likely got a worn component in your syringe, so this will be an easy fix. If you constantly have water in your air line, you may have cross-over, which I've covered previously (https://www.dental-techguru.com/post/curing-the-cross-over-conundrum).
There is a small o'ring inside the syringe which seals around the inner tube of a standard syringe tip. It is through this line that water passes. This small o'ring is what helps keep water in the water line and air in the air passages of the standard syringe tip so the syringe can function as intended. If this o'ring is worn or missing, it can cause water to leak into your air line yielding the difficulty described.
O'ring is #6 in the diagram above is the o'ring in question. Most syringes use a standard o'ring #003 (this is an o'ring industry number) in this location. In order for this o'ring to seal, not only must it be in good condition, but the "adapter" (#5 in the diagram) must be snuggly secured (using a 5/32" hex wrench). The syringe tip also needs to be firmly inserted so that the inner water tube penetrates this o'ring. Many metallic syringe tips have a groove in them which should roughly line up with the front of the nut (#2 in the diagram) when the tip is properly seated. This is one of the reasons I recommend exercising caution when choosing to use disposable syringe tips, as some designs do not have the extended inner water line and require special adapters to seal (I've gone into more detail on this in a subscriber-exclusive series).
To keep your syringe functioning well, I recommend lubricating the o'rings and buttons with silicone-based gel lubricant on a regular basis. Generally, at least quarterly, but some practitioners may need to do so more frequently than that.
I'd like the thank the folks at Beaverstate Dental (https://www.beaverstatedental.com/) for allowing me to use their diagram.