Lots of different setups for AC.
The condenser fan may be on a pressure stat and automatically turns on and off to maintain a specific pressure in the condenser coil. On a cool day it would be off more than on. Called a low ambient control. A freon leak or undercharge can also cause this.
If it's a bad cap, you can of course test the cap but if you don't have a cap feature on your meter, give the condenser motor a spin by hand. Because the capacitor is only used for the start winding, a motor with a bad capacitor will run fine if you start it by hand. One of the symptoms of a bad capacitor is a fan motor that is found running backwards, without a start winding to start it the right way, it will run in either direction.
And of course you can ohm out the motor to check for open windings or a short to ground.
If the bearings on the condenser fan don't squeal, she might have hear the compressor short cycling. Scroll compressors can usually start pretty well under pressure but some compressors need a few minutes for the freon pressures to equalize or they can't get going and can make some odd noises. Adding a delay on break (DOB) or delay on make (DOM) timer can help prevent short cycling which can be caused by all sorts of things.