My computer keeps restarting after upgrading!

Hi guys. I just recently upgraded my computer to windows 8. Before upgrading I've had no problems whatsoever. Yesterday I was surfing the web and my computer randomly shuts off and comes back on. I didn't get a error message or anything. So it's been happening more consistently. So I went to my event viewer I found a critical error saying "The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly."

This is also a copy of the details of the event. If anyone can give some advice on what causing this, I would appreciate it!

- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
<Provider Name="Microsoft-Windows-Kernel-Power" Guid="{331C3B3A-2005-44C2-AC5E-77220C37D6B4}" />
<EventID>41</EventID>
<Version>3</Version>
<Level>1</Level>
<Task>63</Task>
<Opcode>0</Opcode>
<Keywords>0x8000000000000002</Keywords>
<TimeCreated SystemTime="2013-01-28T03:01:13.137618300Z" />
<EventRecordID>660</EventRecordID>
<Correlation />
<Execution ProcessID="4" ThreadID="8" />
<Channel>System</Channel>
<Computer>Enrique-PC</Computer>
<Security UserID="S-1-5-18" />
</System>
- <EventData>
<Data Name="BugcheckCode">0</Data>
<Data Name="BugcheckParameter1">0x0</Data>
<Data Name="BugcheckParameter2">0x0</Data>
<Data Name="BugcheckParameter3">0x0</Data>
<Data Name="BugcheckParameter4">0x0</Data>
<Data Name="SleepInProgress">0</Data>
<Data Name="PowerButtonTimestamp">0</Data>
<Data Name="BootAppStatus">0</Data>
</EventData>
</Event>