I have an Emerson that does the same thing. The cooling fan comes on for about 15 secs. every 20 minutes. I used to switch of the power block when I thought it was the DVD drive spinning up, but now I just live with it.
3 AM ? Uh oh ! I think you are suffering from demonic posession - According to the movie exorcism of Emily Rose, 3AM is the inverse of 3PM, which is the hour Christ was resurrected - So usually demonic manifestations occur at 3AM precisely, like in the movie exorcism of Emily Rose. So that is the problem.
To PROVE this, simply UNPLUG the unit from the outlet, it will still make noises.
I can’t give any further advice mate, but all I can say is…BE AFRAID…be VERY afraid, this is only the beginning.
Get a new recorder or better yet a new house…but don’t take this lightly, it will get worse!
BTW is your DVD recorder one of those models with a hard disk ?