Clothes dryer shuts off after 4 minutes and throws sparks from bottom!!?

Okay. I have an older (1998 model) Kenmore 80 series electric clothes dryer. It has sat and run fine since it was bought new. We've just moved into a new house, and now the dryer will run for only about 4 or 5 minutes before shutting off and shooting 3 or 4 blue sparks from the bottom. For those 4 to 5 minutes of 'run time', the dryer shakes and is extremely noisy, and bounces all over the place. I've checked the bottom legs....it appears to be perfectly level. It heats up like normal. It has never had any problems besides having to replace the element once, about 4 years ago.

Type #: 180-00
Serial #: MH0441499
Model/Stock #: 66812692

Anyone have a clue??