linux frustration

hi all, i'm fairly new at running my own linux server, so i'm hoping someone can offer some suggestions here

i've got a server running redhat fedora... it was running fine until recently it just started hanging / stalling if i left it running for more than a few hours (prior to this, i never turned it off --- because, you know, it's a server)

now it won't even boot up, it gets stuck on "linux decompressing" and does nothing from there.

what was weirder... i left it alone for two days while i was busy with "real life", turned it on to see.. .and it started up... for a few hours and then we started this whole process over.

any thoughts on this?

thanks for any suggestions