Use ExecuteQueryRetry to ensure SharePoint isn't saturated with requests.

while (retryAttempts < retryCount)
{
    try
    {
        // ClientTag property is limited to 32 chars
        if (string.IsNullOrEmpty(clientTag))
        {
            clientTag = "UniqueIdentifier";
        }
        if (clientTag.Length > 32)
        {
            clientTag = clientTag.Substring(0, 32);
        }
        
        clientContext.ClientTag = clientTag;
        clientContext.ExecuteQuery();
        return;
    }
    catch (WebException wex)
    {
        var response = wex.Response as HttpWebResponse;
        
        if (response != null && (response.StatusCode == (HttpStatusCode)429 || response.StatusCode == (HttpStatusCode)503))
        {
            Thread.Sleep(backoffInterval);
            retryAttempts++;
            backoffInterval = backoffInterval * 2;
        }
        else
        {
            throw;
        }
    }
}

clientContext.ExecuteQueryRetry();