I'm pretty sure it's to do with the fan (it happens when cpu being used is high.) Apparently this has happened to quite a few Acers before. Does anyone have any solutions (bearing in mind im a noob)
In advance thanks
Computers have thermometers built in to many components, including the CPU and GPU. If these components reach a certain temperature (often 80-90 degrees for laptops), the Motherboard will automatically power off the computer to prevent any damage to the components. As you said that it happens when the CPU is under strain, it seems this is probably what's happening.
If it's a new laptop and has always done this, just return it. It's probably a manufacturing fault, and could be due to the heatsink being poorly seated, or inadequate thermal paste. If there are no fans running on your laptop, this would also contribute.
If it's an old laptop, it could be due to dust buildup, reducing airflow. You can look in the vents and try to blow out some dust (protect your eyes).
You can monitor the temperature and fan speeds of your computer using Speedfan, which is free to download here. There is a link to the download where it says "The latest version is...".
Like I said, it's almost certainly overheating, and if it's new you should just return it to your retailer and get a replacement. I know that when you get a new laptop the last thing you want is to return it, but seriously - it's not worth the effort of trying to fix it yourself, and it's most certainly not worth the effort of putting up with it for the long term.