I have a Mac Mini that has been sitting on shelf as a server for about 6 years. It is a MacMini5,2 with 2.7Ghz Intel Core i7 and 8Gb of RAM, 500Gb HD running Sierra. Recently is has been slowing down. Every action takes an interminable long time and I end up just restarting. More recently it has been just restarting (well, crashing) by itself. I have just finished moving all it's services (DNS, Confluence, Jira) off to another server and thought I would look into the issue. It's not a hard drive or system issue. I've rebuilt a fresh system from scratch on a new external hard drive (internal removed). It's not RAM as I've swapped it out. I have run Memtest and it comes up clear. I'm thinking heat, and have Martin Bresink's Hardware Monitor running on it. Not seeing anything drastic (although it also hasn't crashed since I began monitoring). I checked the fans and heat sinks for dust when I pulled the hard drive. Any other suggestions or possibilities?