Colbyt wrote:

Don't know that brand or whether or not it is electric. I will
assume it is electric.

You either have a defective thermostat or a defective "high limit"
control.
You may be able to test for the defective "high limit" control by
bypassing it on a temporary basis.

I want to be clear about this:

BYPASSING THE SAFETY FEATURE IS FOR TESTING PURPOSES ONLY.
USING THE HEATER WITH A BYPASSED CONTROL IS STUPID AND DANGEROUS.

So is hypothermia.