High-pitched whine AFTER playing vinyl

Newbie warning: I'm just getting started so forgive me if I say/ask something dumb.

A while back, I decided to start ripping some of my dad's old out-of-print vinyl to CD for him for a Christmas gift so he can listen in the car. As a result, I caught the vinyl bug. Now I'm hooked.

Here's what I bought:
Technics SL-1210 MK5 (brand new)
Denon DL-160 (HO MC)

That's all I can afford right now.

I'm listening through an Onkyo TX-NR801 receiver. It has phono inputs and a built in phono stage. Specs say it has a S/N ratio of 80db.

I think I have it set up correctly. I followed all the TT and cartridge instructions. All this old vinyl never sounded so good! I'm amazed!

However, as soon as I lift the stylus off the record (always using the cue lever) there's this high pitched whine or squeal that lasts for 15-30 seconds and then goes away. It sounds like a UFO landing. It starts really high pitched then lowers right before it goes away. It's only after I've played something that it does it. It's not present during record silence between tracks. I can play a record for a split second, raise the arm, and it still does it.

I've got the TT grounded to the receiver and I'm not getting any hum whatsoever. It's not coming from the mechanics of the TT because it does it whether or not the table is spinning. I can even completely power the TT down and it will still squeal through the outputs for its normal 15-30 seconds.

I only have about 3 hours of play on this setup. Is this part of breaking-in a cartridge? Any help would be appreciated. I've been playing lots of 45's so this whine is getting old fast since I hear it after every record.

Thanks in advance!