List all your emulators:
emulator -list-avds
Run one of the listed emulators with -avd flag:
emulator -avd @name-of-your-emulator
where emulator is under:
${ANDROID_SDK}/tools/emulator
Mine:
Pixel_2_API_29_And10
Pixel_4_API_30_And11
Pixel_4_API_S_And12
To start an Virtual Device:
# Start multiple devices:
emulator -avd Pixel_2_API_29_And10 Pixel_4_API_30_And11
# To start one:
emulator -avd Pixel_4_API_30_And11