External enclosure way cooler than inside pc

i had my 3500a in a Bytecc usb 2.0 external enclosure previously, and i burned about 70 dvds consecutively and none of em were warm at all; in fact they were cool. But I put the nec in my pc for a firmware update. Installed it fine, and flashed it without a hitch. Burned a few dvds flawlessly but after i burn about 3-4 the drive and the dvd itself gets pretty warm…is that normal? I’m just considering popping it back out and slap it in the enclosure but if its normal I can live with it.

it is normal