Automatic Shut Off

Have you gone into the menu settings and checked the auto shut off time?

Have you try with lower heat setting?
It seems like it might be thermostat or thermal fuse that is not working properly.

It will most probably need an overhual of the power supply

Check that you have not got an auto power off setting on. Check that the aerial connections are good. That the signal is strong from the stations it is picking up. Weak signals can cause the box to shut down.
It the box is very hot when it shuts down, you might have a fault on it.

Most likley what it could be is an interferance in the TV. Modern TV's have a feature that will shut itself off when it is not receving a picture. For instance, after so many minutes of "snow" it will shut off.sometimes this can make the TV think there is no signal at shut itself off.Anyway, I suspect its an interferance issue. Perhaps moving the TV further from the source of the interferance might help.

Enter in the user mode:
1.Press the Clear mode key.
2. Press the Clear/Stop key more 4 sec untill the user tool menu appears on the touch panel.
3.This copiers has more 12 user tools.You can see 5 user tools on the display at the same time.Use these keys to see the rest .
4.AUTO RESET: the copier return to the initial condition autommatically after your job is finished.(after 60 sec)
5.SCREEN SAVER :when the copier does not detect anyone operating it for selected time the display turns OFF.(60 sec).
6AUTO OFF:Whwn the machine is used after weekly timer has turned it OFF the copier will turn itself back OFF after the selected time.The auto OFF time can be set from 1 to 999 minute or the function can be turned.(I recomanded setting level OFF).

If the period of time in question is reasonably consistent - say 45 minutes after powering up it shuts off - you could be suffering from an overheating issue inside the unit. Temprature sensors can override manual operation and shut the unit off to avoid greater damage (or even a fire) occuring. Have the TV serviced.
If you find it happens at random time intervals from cold this is less likely to be the case and it could be relative to the mains power supply going to the TV. If you suffer from 'dirty power' (power that dips and surges instead of giving a consistent voltage) this could also cause an automatic shutdown condition within the TV. This could happen at any time after the unit has been turned on. An unterruptible power supply (UPS) would help with that.

You have to use the "Auto-Off" feature, which is located on the same button as on/off:
The automatic shutoff time (ASO) can be
programmed to shut off immediately after
brewing (0:00) or up to 4 hours later. The
default shutoff time is 2 hours.
Press and hold the On/Off button to display
current shutoff time. To change the preset
time, press and hold the On/Off button until
the red power light and LCD display begin to
flash. This signals that you have entered the
Set automatic shutoff mode. Set the time
you want coffee to begin brewing by
following the instructions in “Entering Time
Set Mode.”
When the coffeemaker shuts itself off, two
tones will sound.
NOTE: Automatic shutoff may be
programmed either before or during coffee
brewing. If you program the auto shutoff
time after brewing is completed the unit
will automatically account for elapsed time.
For example, if you set the auto shutoff for
40 minutes and 25 minutes have already
elapsed, the unit will shut off automatically
after 15 minutes (40 minutes minus the 25
elapsed equals 15 minutes).

-Tha Mp3 Doctor

If it's staying on for just a short period of time it sounds like there is a sensor that is giving the unit a faulty condition (Perhaps for reason or due to a fault in the sensor). There are normally a few temp sensors in the TV around the Lamp and Ballast. They may be bad, or the lamp or ballast is just generating too much heat.

I would guess your light should dim after 5 minutes. But I bet your axim wont shut off for 2,3, or 4 hours. My battery is wonderful so I have it shutting off after 2 hours.