Choppiness with empty template project on Android

Android
1

I own a budget Android smartphone, but even it should be capable of running an empty project without choppiness.

The draw method has this code:

if (gameTime.ElapsedGameTime.TotalMilliseconds > 20)
{
    GraphicsDevice.Clear(Color.Gray);
}
else
{
    GraphicsDevice.Clear(Color.Black);
}

base.Draw(gameTime);
gameTime.ElapsedGameTime = TimeSpan.Zero;

The choppiness manifests itself as the screen blinking grey roughly once every three seconds. In another project, a square controlled by the accelerometer moving around the screen, the choppiness can be seen in the movement of the square.

The phone is a Coolpad Rogue, running Android 5.1.

The choppiness seems somewhat regular in interval. Could it be related to garbage collection?