According to the literature, there is a significant number of inflationary models that lack observational and conceptual support. Such is the case with recent observations regarding a possible preferred direction in the universe, which imply that scalar fields are not suitable as generators of inflation. On the other hand, recent inflationary models that employ vector fields require a modification of gravity and/or fine-tuning in order to have the appropriate behaviour; besides, they lack naturalness and do not exhibit one of the most important properties of theories in modern physics: the existence of internal symmetries. In this paper, we present a vector inflationary model embodied in a SU(2) gauge theory composed of three vector fields over which we make a well supported assumption about their direction, their norm, and their time dependence. Such an assumption allows us to obtain isotropic inflation in a rotationally invariant background if we take into account the homomorphic relation between SU(2) and O(3) groups. In this scenario, we study the dynamics of the vector fields and the conditions to obtain accelerated expansion; we also analyze the evolution of the system in the slow-roll regime and obtain numerical solutions for the equations of motion. Due to the naturalness of the model, the observed numerical results and the generality of the proposed assumption, we conclude that this type of inflation represents well the behaviour of the primordial universe in view of the most recent observations.