So are you using Shared hosting? Well if your a startup, you shouldn't really be on shared hosting to begin with.

I would recommend you look into getting a VPS or even a dedicated server if you can.

There could of been a chance that your current server was getting DDOS'd, but there's not much you can do about that unless you get DDOS protected hosting. You can also look at setting up CloudFlare, which will cache your site if the main server decides to go down.