CDJ 350 switches itself off after a few minutes

Hi,

one of my CDJ 350s started turning off on his own today. 

I started it, it said "ejecting" (it has no CD in it. In fact, it never had). It then made some sounds and went to standby. I tried it 4-5 times, always the same. I then tried to force-eject it. Now i have the same problem, the only difference is, that the CDJ tries to LOAD a CD now. The CD/eject button glows all the time. 

If i manage to push the USB-button right at the start, i'm able to play music from my USB for about 5 minutes, before the cdj switches to standby again. If i don't push anything at the start, it just freezes and also goes to standby.

Oh, and sometimes it starts itself again - even if i just pulled out the cable - just to go to standby once again shorty after.

I really hope you can help me :).I have no warranty left and not that much money (and time) left for a mechanical repair.

UPDATE:

The CDJ seems to work pretty normal now, but it still shuts off after a few (something between 3 to 10) minutes.