Server shuts down after a while

So, everyday, I set up a server, it takes a really REALLY long time, and after it loads, everything is all laggy, and it's just eeuugghhh.

THEN, it just crashes/shuts down

I have no idea why this happens, can someone help/explain why this is happening?

Software? not sure what you mean by that, but, I am using the Java Edition on pre-7