Kindle wont turn on,half boots when plugged in? definately motherboard

Basically,

Kindle shut off. became unresponsive. If i plug it in it gets to the 'kindle fire' screen then turns off after 4 seconds. Ive tried all resets to no prevail. I decided I would pry off the back and check nothing was loose in the motherboard, after blowing the dust out and pushing everything down the kindle rebooted and started! I replaced the back and then tried to turn it on again..same problem as before, unresponsive! guess my question is, which part of the motherboard is causing this problem?! as i know its something loose as it restarted before! please help! thanks :)