I have an old (20 year old) Intertherm Electric Furnace, Model FEH-012HA, 240 volts ac, 41,000BTU, Single Speed Blower Motor 2.5 FLA 1/8 HP. It will run fine, heat the home, but sometimes fails to come back on again without kicking the breakers for it in the main breaker box from on to off and back on again. After doing this the furnace will come back on again and run normally. I have replaced the thermostat and the breakers in the main breaker box and the fuses are fine in the furnace but it still does it and I am getting tired of waking up cold in the middle of the night. Anyone have any ideas as to what my problem could be?

When these FEH's get older, the sequencers will wear out. The fan doesn't come on properly, and then the electric heater inside is damaged. The electric heater sags down, and hits the metal on the framework holding up the heating coils. This will blow the fuses, or pop the breaker(s).
The heater will eventually short bad enough that it will explode. Leave the unit powered off!
Have a Professional change out the Sequencer, and pull the heater. I'm guessing it's the one on the bottom. You will likely need a new one. Once that is changed out, it will work good.
Good Luck, and always be safe.