Most common things are Thermostat or a bad heater core but could also be something blocking the door down by the heater core. I changed my Thermostat and Heater control Valve to find out a pencil fell in the defroster and prevented the door from closing. Hope this helps.
Check the condition of your heater core.
It's obvious that you have problems with wiring. I would start from the heater/AC control panel.
A short circuit.
Will a 1998 Toyota Camry motor fit in a 1999 Toyota Camry
No, it will not.
The blower motor resistor is defective.
Tire out of balance or bent wheel.
Could be your timing belt.
Yes. Both Toyota and Camry are proper nouns (brand name and model).
Toyota Camry coil wire can burn out from age or excessive use. The manufacturer recommends that you change the coil wire every 30,000 miles.
That would depend on many things. The year of your Toyota Camry, engine size, and how you drive.
Toyota Camry