How can I auto start chat in preChat(LWC) when the page loaded and the condition is true

How can I auto start chat in preChat(LWC) when the page loaded and the condition is true.  

 I tried to do the code below

import BasePrechat from 'lightningsnapin/basePrechat';
import { api, track } from 'lwc';
import startChatLabel from '@salesforce/label/c.StartChat';
export default class Prechat extends BasePrechat {
    @api prechatFields;
    @api backgroundImgURL;
    @track fields;
    @track namelist;#Chatbot
    startChatLabel;
    test = 'test';
    // test = '';
    connectedCallback() {
        this.startChatLabel = startChatLabel;
        this.fields = this.prechatFields.map(field => {
            const { label, name, value, required, maxLength } = field;
            return { label, value, name, required, maxLength };
        });
        this.namelist = this.fields.map(field => field.name);
        if (this.test != '') {
            this.handleStartChat();
        }
    }
    renderedCallback() {
        this.template.querySelector("lightning-input").focus();
    }
    handleStartChat() {
        this.template.querySelectorAll("lightning-input").forEach(input => {
            this.fields[this.namelist.indexOf(input.name)].value = input.value;
        });
        if (this.validateFields(this.fields).valid) {
            this.startChat(this.fields);
        } else {
            // Error handling if fields do not pass validation.
        }
    }
}

 But the error below occurs

How can I solve this problem?  Thank you! 

#Salesforce Developer