So, your site is slow, then fast. It works, then it doesn't work.
If this is happening to you, the likely culprit is DNS.
Propagation
If you recently changed your name servers or DNS, then you are in a 48 to 72 hour period known as propagation. Once propagation is over, your site should be stable.
DNS Glue
If you are using private name servers, or have stopped using private name servers, then you need to make your NS records in your domain's DNS zone match the new name servers you are using.
Please read more in the related article.
Other
If neither of those situations apply to you, please contact HostGator support so we can evaluate the situation.