Turning off randomly

Overheating can be one of the problem. Also try removing any usb port connections [printer,scanners,pen drives etc.]. Use the laptop where ventilation is good. Download this program..."EVEREST" to check the temperature and other system information from here http://www.majorgeeks.com/download4181.html Do not try to blow air as the dust might affect cd-reading capability of your laptop's lens.You can refer to these images on how to disassemble
http://www.insidemylaptop.com/disassemble-sony-vaio-tz-laptop-remove-hard-drive/ if you can somehow protect the lens by covering it up with something then you can blow some air inside to clean of the dust specially on the CPU area,you might also want to apply a little thermal paste [you can get it from a computer hardware store] Hope that will do otherwise I would recommend you to show it an authorized service personel.

your cooling fans probably arnt working