My playstation turns on for approx 15 seconds then turns itself off again, whats wrong?

Thermostat issue when it reaches heat its set to it should turn off and then come back on when it drops below that temp
check if thermostat is clean

Are you still having this problem?

sounds like the clutch on the compressor

Hardware problems, most likely caused by overheating processor ; Install this program and monitor your pc - if something is wrong you will see it and know what to fix
http://www.almico.com/speedfan.php

Before connecting the ethernet cable to the back of your Playstaion3 hold the modem reset button for 15 seconds, when 15 secs are up connect the ethernet cable to your ps3 system, wait until tour Comcast High Speed Internet goes online again (all the lights are showing fine) then try setting up your Playstation connection settings again, it might work since now you have reseted your modem and the modem will send information to new device, I hope this information works for you, :)

This could be due to bad capacitors in the sweep supply, a bad High Voltage block, a bad regulator.

A stuck color wheel can cause this exact problem.

Remove the battery for 15 minutes, connect the AC Adapter and install the battery again.
It that doesn't work, remove the battery again, wait 15 minutes, install it and plug the AC Adapter.
It's a weird problem but in my PSP i get around that way.

The lamp almost always causes this problem. The Sony lamp when about to fail will cause the unit to power off interminttently. Replace the lamp and this will correct the problem.

cold sorters that means needs to sorter it again