A4988 settings for microstepping

I’m using an A4988 with a #1205 stepper (3.8 V, 670 mA). I set the current limit on the A4988 to ~670 mA and turned on 1/16 step microstepping. However, I noticed that when I set my power supply voltage to be > 10 V and microstep slowly, the motion is kind of jerky, so I’m not sure whether it’s correctly microstepping. It’s a lot smoother if I set it to ~7 V, but then again that’s below the minimum supply of 8V.

What are the optimal current/voltage conditions for microstepping?

some background questions to tease more info:
What kind of microcontroller are you using to send the A4988 the “step” commands? And are you powering it with the Vmot input voltage?

What are you using to “set” the MS# pins? Are you simply connecting it to the MCU pins and enabling them HIGH or LOW, or are you just using wire to jumper VDD to the pins as needed?