Hello there,
Your problem could be the server itself, is your new server better than the last one? If not, it might be related to cpu usage or lack of memory.
If the server is good enough, it might be a misconfiguration on file permissions or it might also be the case that the server does not meet your website requirements, like different mysql version, php version or Nginx (apache).
Send me a message, I can troubleshoot your problem and fix it.
Have a good afternoon. (night)