702.1. Turn-based actions are game actions that happen automatically as the turn progresses. It is not possible to handle other effects until the turn-based actions have been dealt with.
702.1a Abilities that watch for a specified step to begin are trigger abilities, not turn-based actions.
702.2. Whenever a step begins, if it’s a step that has any turn-based action associated with it, those turn-based actions are automatically dealt with first. This happens before state-based actions are checked, and before trigger abilities are resolved.
702.3. The turn-based actions are as follows:
702.3a The active player untaps their cards in the battle zone and mana zone simultaneously. Then all the trigger abilities that trigger at the start of the turn are resolved.
702.3b Immediately after the draw step begins, the active player draws a card.
702.3c Immediately after the attacking creature declaration step begins, the active player will attack the designated target.
702.3d Immediately after the block creature designation step begins, the non-active player blocks specify the creature.