If its not showing signs of overheating (Hot to the touch, fans making strange noises if present) aside from the rebooting, odds are you do have a slightly different hardware issue on the go... Acer actually has a bit of a bad rap (Understatement) in their laptop/mobile markets here in North America, and largely with good reason. Their laptops and mobiles have a strange habit of falling apart (Literally, the casements break/fall off quite easily, even without being abused in any way; and its not covered in warranty even though its known they use fragile plastic) and over heating. Their overall designs are good and will generally work, however they seem to cut costs by using some sub-par parts in manufacturing (Thats how they keep their equipment relatively cheap), which leads to a high failure rate in them. Its these sub-par components that tend to cause issue with Acer based systems (And is why you have some people who swear by them while a lot of others refuse to deal with them)

In the case of this guy, if it is hardware, its probably improper/damaged soldering points (Not making a proper connection) right on the devices system board causing a short, or else a bad component/component failure (For example, it might be a case of bad sectors on the ram, and when it goes to write to the bad sectors, it crashes, this one usually gets a BSOD, but there are failures that don't always get them)... both these issues are not exactly something you would want to check into yourself (Its a pain in the ass, I wont do it for someone without charging double time, and it isn't a quick process), so your best bet is to fight with Acer for a replacement/free repair.