Post a few more details if you wouldn’t mind.
Is it a shared hosting environment?
If so, you obviously are limited by what your host is prepared to do for you.
If it is a VPS or dedicated (or you have access to apache/php/mysql)
You need to look into why you are having to reboot the system daily. Begin by looking at the obvious, post the output of
# free -m
This should give an insight into the load on the server.
Failing that, (insert shameless advert here), get in touch with us for some specialised Magento hosting.