I think I sprayed too much primer for my first coat when painting my cabinets. What should I do next?

The smoother it is before each coat, the better the coat will look. I run my fingers over the surface while sanding to find and remove imperfections that aren’t visible.

If 120 grit is slow, go with 80 grit, then 120, then 240 and finish with 320 or even 400. For between coats you should only need a very light sand with 400.

(Instead of buying 400 grit, you can keep your used 320 grit since they get smoother before becoming useless).

Painting requires patience and practice. All paint behaves slightly different and the air temperature/humidity will also affect it.

You've got small globs there which means the primer went on too thick. Try a coat thinning it a bit. Wagner always say no thinning is necessary but I've thinned almost every thing I've ever sprayed. Always start the spray away from the work and then draw it across the work, past the work to stop or continue back over for the next pass. You want light coats and move the sprayer fairly fast over the work. Very light sanding is all you should need between coats if you do it properly. Practice a bit more and you should be OK.