bought a new memory stick online

Hi,

 

I purchased a new memory stick online at amazon and when I plugged it in my computer the computer did something, I'm not sure what. And then when I was watching a movie on itunes for seemingly no reason the computer rebooted on its own. Its the first time its done that. I could still watch the movie, it was buffered on apple tv. But it just seemed weird.

 

I've run scans and nothing has been found, but I'm still kind of anxious about it. Should I be looking for anything?