Why does my pizza dough rise so inconsistently?
If the yeast isn't out of date then the most likely sounding culprit is the temperature of your water.  It should be between 105-110.  If it's too cool then you won't activate the yeast and if you get it too warm you'll start to kill it.

Another possible case can be when you're adding the salt. If it's going in before or at the same time as the sugar you will arrest the gas production and activity of the yeast.

Get the yeast, sugar, water mixture going first and create a shaggy dough with your flour.  Add the salt as you're starting to bring the dough together so that it doesn't act too quickly to arrest the yeast development.

If you keep your flour in the freezer or refrigerator, make sure it has come to room temperature before adding it to the water or the chill of the flour will de-activate the yeast.