two minute shutdown

Recently for no reason I can think of my Mac has started shutting down after about two minutes of inactivity but if I am doing stuff on it it is fine. I did some research on similar problems on the web but they were more to do with fan and power failures which I do not think this is due to it being after a period of inactivity and the fact it asks if I am sure I want to shutdown or whether I want to cancel. If I do not press cancel or move the mouse in about five seconds it automatically shuts down despite this screen. This leads me to believe that it maybe a setting I have changed or whether you think it a hardware fault. So I was just wondering if anyone can help me solve this problem as it would be greatly appreciatedas at the moment I can't leave my mac unattended for longer than two minuted and it is getting really annoying.

It would help if you would tell us something about your machine....

First, make sure that you have set all your power options from System Preferences.

Next, try doing a SMC (System Management Controller) reset. Follow the directions given in this Apple KB LINK. If that doesn't resolve the problem, post back and we'll go from there.

Regards.

the first solution didnt work as it was telling me it was set to half an hour but it shuts off after two minutes. As for the second solution it doesn' cause any memory loss or anything like that does it?

Since the first thing you have to do for the SMC reset is turn your machine off, everything that was in memory is already gone. So, the answer is no, it doesn't.