[the Sandman]

If the problem happens again then you will need to move to a dedicated server where you would have all the resources you need for your site and if you overload something it will only affect your account not 150 others which are present on a virtual machine.

Hmm, that seems excessive.

It is possible that your server was not optimized, or was configured incorrectly, that you've added modifications which have too many queries or are otherwise inefficient, or that your files or database are corrupted in some way causing you to overtax the server's resources. Maybe you're just grown to the point where you do need a semi-dedicated or dedicated box. This should be looked into, but in the meantime you should consider changing to a different hosting service whatever the cause.