Laptop sometimes reboots itself at shutdown

I hope someone can help me with this problem. I saw a previous thread about a PC that would reboot on shutdown, but it didn't seem to be the same problem as mine.

I've only had this laptop four months, but it's always done this. When I shutdown, sometimes it will reboot itself and then show the error message 'Windows has recovered from an unexpected shutdown'. Details:

Problem signature:
Problem Event Name: BlueScreen
OS Version: 6.0.6001.2.1.0.768.3
Locale ID: 2057

Additional information about the problem:
BCCode: 9f
BCP1: 00000003
BCP2: 8794F870
BCP3: 86AB1030
BCP4: 8EE48E00
OS Version: 6_0_6001
Service Pack: 1_0
Product: 768_1

Files that help describe the problem:
C:\Windows\Minidump\Mini111308-01.dmp
C:\Users\...\AppData\Local\Temp\WER-44959-0.sysdata.xml
C:\Users\...\AppData\Local\Temp\WER3004.tmp.version.txt​

Often I go back to switch my laptop on and have to plug it in to the mains just to get it started, because it's rebooted and simply run out of power when I'm not around. I thought at first it might only happen when I updated or installed new stuff, but it's not that. It doesn't happen every time I shutdown either, and it never shuts down unexpectedly. The Microsoft Problem Reporting doesn't have a solution to this. I have also tried setting it to power off when the lid is shut and closing it after I have clicked shut down, but it doesn't stop it rebooting.
Any help very much appreciated!