Symfony 2 boot requires a lot of time

[dog199200]

I've tried to deploy my symfony 2 project to the shared-hosting that I have (aruba.it) and that will run my website (no chance to change provider or get a vps/dedicated server). My problem is simple but really big: the first time I open the site after not using it for a bit of time (15 min for example) the first request is too much slow (15-20 seconds of loading). It's a long time, the user can't wait a so long time before seeing the homepage. I though that the problem could be that the php compiled code is purged from the RAM and so symfony will have to reboot. Anyone has these problems? Any help appreciated