Mathf.LerpAngle

Description

Same as Lerp but makes sure the values interpolate correctly when they wrap around 360 degrees.

The parameter t is clamped to the range [0, 1]. Variables a and b are assumed to be in degrees.

using UnityEngine;

public class Example : MonoBehaviour
{
    float minAngle = 0.0f;
    float maxAngle = 90.0f;

    void Update()
    {
        float angle = Mathf.LerpAngle(minAngle, maxAngle, Time.time);
        transform.eulerAngles = new Vector3(0, angle, 0);
    }
}

Additional resources: Lerp.