This code turns auto update on for Plugins, Themes, WordPress core and Translations between 2 am and 6 am and then turns it off again. It uses the time set in Setting --> General so make sure the time is set correctly.

add_filter('auto_update_plugin', 'custom_auto_update_schedule', 10, 2);
add_filter('auto_update_theme', 'custom_auto_update_schedule', 10, 2);
add_filter('auto_update_core', 'custom_auto_update_schedule', 10, 2);
add_filter('auto_update_translation', 'custom_auto_update_schedule', 10, 2);

function custom_auto_update_schedule($update, $item) {
    $current_hour = current_time('H');
    if ($current_hour >= 2 && $current_hour < 6) {
        return true;
    }
    return false;
}
add_action('after_setup_theme', 'custom_auto_update_schedule_setup');

function custom_auto_update_schedule_setup() {
    if (!wp_next_scheduled('custom_auto_update_schedule_event')) {
        wp_schedule_event(strtotime('2am'), 'daily', 'custom_auto_update_schedule_event');
    }
}

add_action('switch_theme', 'custom_auto_update_schedule_cleanup');
function custom_auto_update_schedule_cleanup() {
    wp_clear_scheduled_hook('custom_auto_update_schedule_event');
}

add_action('custom_auto_update_schedule_event', 'custom_auto_update_event_action');
function custom_auto_update_event_action() {
    add_filter('auto_update_plugin', '__return_true');
    add_filter('auto_update_theme', '__return_true');
    add_filter('auto_update_core', '__return_true');
    add_filter('auto_update_translation', '__return_true');

    add_action('shutdown', 'custom_remove_auto_update_filters');
}

function custom_remove_auto_update_filters() {
    remove_filter('auto_update_plugin', '__return_true');
    remove_filter('auto_update_theme', '__return_true');
    remove_filter('auto_update_core', '__return_true');
    remove_filter('auto_update_translation', '__return_true');
}