Just because it was bought on line doesn't mean anything- unless of course if you don't have an Apple store any where near you that's a different story.. If that's the case have them send you a box for you to return it in.. If it's new- you shouldn't have to worry about troubleshooting.. You paid Apple to do that- use it..
I brought my iMac to Apple last week because I wasn't happy with the temperatures.. The memory control runs at 175f when it's turned on- not working hard, just not sleeping.. They had it for hours and did every test under the sun.. It passed, and apparently it was fine- but the point is, that's why they're there and they did it with a smile on their faces and actually really tried to see if they could find anything..I know I looked like the biggest tool in the shed, , using Apple Care when it turns out there's nothing wrong with my computer, but I don't care, that's why you pay for it..