Recently had a lady with a sony laptop that had a faulty fan and was overheating and resetting. This was a known fault with these laptops, and sony repaired the laptop free of charge even though the warranty had expired. All that had to be done was to ring them and then get it sent to Auckland. So if your sony laptop is overheating and resetting itsself then give the sony support center a ring.
Sometimes after you have had your laptop for a few years you can be using it and then it can suddenly restart, and then you turn it back on and it can keep restarting. if you feel your laptop to see how hot it is you can often feel that it is quite hot through the plastic.