Why is it happening?
There may be multiple reasons for the Toshiba laptop charger becoming overheated. One could be that the power adapter is too weak in wattage for the laptop. For example, if you have a 90-watt adapter and it is heating up, check with Toshiba to see if you can use a 120-watt adapter. Also if you are keeping your laptop plugged in while running power intensive components, such as more demanding tasks for your CPU and GPU, then your Toshiba will drain power from the charger more quickly, possibly causing it to become hotter.
When the laptop charger becomes overheated, it may be an indication of the AC/DC converter beginning the fail. The AC/DC converter turns the current from alternating current, from your electrical outlet, to direct current, which is the form of electricity used by your Toshiba laptop. Overheating also can damage other internal components. The solder joints may only have partial contact due to heat expansion and contraction.
Check Toshiba's website for potential recalls on the charger or your computer. Look for the model number and serial number from your laptop and charger and see if either of the two are currently being recalled.
Give the Toshiba laptop charger more exposure to the air when it is being used. You may want to put some pens, or other small objects, underneath the charger so that it has more air circulation. Turning the charger on its side will also help expose the charger to more air circulation. Never leave the laptop plugged in unattended because there is risk of fire. If you detect burning smells coming from the Toshiba laptop charger, you should unplug it immediately and monitor it until it cools down. Contact Toshiba to see if they will replace the charger and explain that it was giving off a burned odor.
Do not put the hot charger near upholstery, blankets, pillows, cushions or paper. Anything that can catch fire quickly and easily should not be within reach of the charger.