The restart may be overheat related. Does the sound it's making sound sort of like a small fan rubbing on something at high speed or a whine like a fan with bad bearings? If so, perhaps your fan isn't working properly and your box is overheating. You can search the web for replacement parts, but you may have luck with this link:
http://www3.goldenshop.com.hk/AI-trad/d-main.htm