If you want to Enable COD Payment Method for Particular Products, Follow below steps

You need to create an extension for this,

Here I have created extension : Magemonkeys_CodRestrict

1. Add new YES/NO product attribute i.e enable_cod_payment and set in Attribute Set which you are using for products

2. Create registration.php file in app/code/Magemonkeys/CodRestrict and add below code

<?php
MagentoFrameworkComponentComponentRegistrar::register(
MagentoFrameworkComponentComponentRegistrar::MODULE,
'Magemonkeys_CodRestrict',
__DIR__
);

3. Create module.xml file in app/code/Magemonkeys/CodRestrict/etc and add below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
	<module name="Magemonkeys_CodRestrict" setup_version="1.0">
	</module>
</config>

3. Create module.xml file in app/code/Magemonkeys/CodRestrict/etc and add below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
	<module name="Magemonkeys_CodRestrict" setup_version="1.0">
	</module>
</config>

4. Create events.xml file in app/code/Magemonkeys/CodRestrict/etc and add below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="payment_method_is_active">
        <observer name="codpayment" instance="MagemonkeysCodRestrictObserverCodAvailable" />
    </event>
</config>

5. Create CodAvailable.php file in app/code/Magemonkeys/CodRestrict/Observer and add below code

<?php
 
namespace MagemonkeysCodRestrictObserver;
 
use MagentoFrameworkEventObserverInterface;
 
class CodAvailable implements ObserverInterface
{
	/**
     * payment_method_is_active event handler.
     *
     * @param MagentoFrameworkEventObserver $observer
     */
    public function execute(MagentoFrameworkEventObserver $observer)
    {
        $objectManager = MagentoFrameworkAppObjectManager::getInstance();

		$cartObj = $objectManager->get('MagentoCheckoutModelCart');

		$cartItemsCollection = $cartObj->getQuote()->getItemsCollection(); 

		$cartItemsVisible = $cartObj->getQuote()->getAllVisibleItems(); 

		$itemsArray = $cartObj->getQuote()->getAllItems();
		$enable_cod_payment = array();
		foreach($itemsArray as $item) {
			$productid = $item->getProductId();
			$product = $objectManager->create('MagentoCatalogModelProduct')->load($productid);
   			$enable_cod_payment[] = $product->getData('enable_cod_payment');   			
		}


        if($observer->getEvent()->getMethodInstance()->getCode()=="cashondelivery"){
			if(in_array(0, $enable_cod_payment)){
	            $checkResult = $observer->getEvent()->getResult();
	            $checkResult->setData('is_available', false);
	        }
    	}
    }
}

You can change payment method condition as per your need.