Macbook randomly restarting when plugged in

In the past week, my Macbook has started randomly restarting when it is plugged in. If I put it into sleep mode, it doesn't do it, but if I just leave it on, it will restart within 15 minutes. I can't think of anything I have done or installed lately. I have searched for software updates and installed the recommended ones with no luck. Any ideas?

Thanks!

Wendy

You didn't supply us with much info about your MacBook and what version of OS X you're running. But briefly, random restarting can be caused by bad memory, a defective power supply, or overheating. As for the overheating, make sure your fan is operating. Can you hear it?

Sorry about that! Here are the specs:
MacBook 2.4GHz/ 4GB ram/ 250GB HDD

I'm running Snow Leopard 10.6.4

I am not noticing the laptop getting hot, but I have not noticed the fan running either. I'll have to pay closer attention and try to see if I can hear it. I only notice the restarts when it is plugged in.

How would I know if it is bad memory? Is there something I can look for, or do I need to have it looked at?
Thanks!!

Wendy

I am not noticing the laptop getting hot, but I have not noticed the fan running either. I'll have to pay closer attention and try to see if I can hear it. I only notice the restarts when it is plugged in.

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Thanks for posting back the specs. If your MacBook is running OK when it's on battery and only restarting randomly on AC power, it may be a problem with the power supply or the MagSafe Adapter. Since the MagSafe Adapter is easier to swap out, see if you can borrow one from a friend and use it for awhile to test if the rebooting occurs again.

Let us know and we can go from there.

Thank you so much. I'll work on getting a loaner cord and testing it.

Wendy