For the past couple of days, gas dryer wasn't drying clothes thoroughly in one cycle. I had to run the dryer in two to three cycles to dry clothes. As of this weekend, there was a strange burning smell coming from dryer as if some plastic or rubber burned. There was no smoke, only a strong odor of burning. I didn't run dryer again for fear that something may be very wrong. Checked lint trappers/vent in back of dryer and in front, and both are clean. Drum does turn, so belt is okay. What could be the cause of the burning smell and dryer not drying clothes properly?

Please help!

Thanks.