It could be some sort of a buildup within the handle that prevents it from turning smoothly, or it could be an issue with the cartridge.

It's a couple months old what should I look for to see what's causing the issue

Shut the water off, take the handle off, take the stem out, and inspect it, maybe you see something that is preventing it from operating smoothly... You can try calling the American Standard Service department to see what they say.

I had to replace a new installation of the tub faucet/shower handle in a previous home. I had trouble with "mineral"deposits at that home. I'm pretty sure the "mineral" deposits were silica from the water supply which was on a well. The tub faucet had knobs for hot and cold and a third knob to turn on the shower head. The shower selector handle froze up during a period of non-use as the bath was a guest bath. Even after removing the fixture, I had to cut the metal around the valve to finally break the valve free. It was junk after that but I wanted to investigate the problem. After that event, I made sure to operate the valve occasionally to keep it from freezing up in the new fixture.