Heaters runs for a few minutes then shuts off.

99% of the time if ALL power is lost then comes back it's dirty battery cables.

You don't have gas supplied to the heater. It sounds like you have a gas powered unit and the clicking you're hearing is the sparker sparking.

there is also sometimes a photo sensor in the cabinet that detects the flame as a back up to the thermo couple...if this is bad the circuit board control will shut off the gas valve.

safety switch is opening and closing, or issue with gas valve coils

It could be a number of things, bad fuel ( stale) engine over heating and causeing vapour lock, or a bad ignition unit, start with fresh fuel, replace the fuel filter in the tank, try just slackeing the fuel cap and try starting again, this will rule out the fuel tank breather, if still no better replace the ignition unit.

You have activated the alarm. The the ignition on , don't start, let it sit for ten minutes. turn off for five seconds, start the car

indicates a failing coil or ignition control module
internal components over heating and causing the problem

It's possible the thermal reset is defective. It shuts the motor off if it gets hot. Remove the bag door and take the bag off, remove both filters and then turn the vacuum on, just leave it sit there with the motor running. This eliminates the bag or filters causing any airflow resistance. If it still shuts off after a few minutes it's likely the thermal reset is bad. Some vacuums have an external thermal reset button which can be replaced if necessary but on your model it is built into the motor and you must replace the motor. If the motor runs fine put the bag and the filter under the bag back in - (make sure the filter is clean and not restricting airflow) put the bag cover on then turn it on again. If it overheats and shuts off then you may have a clog on there somewhere restricting the airflow. If so check the power nozzle area, the hose coming from the power nozzle, the extension hose and wands for clogs or restrictions.

Check the air lines going to air pressure switch for cracks or splits. I know that will affect the gas valve but not sure if that is your problem.

your unit is undersized or you do not have enough gas supply to run the unit properly.
If you have to many water features running or you have to many gas items turn on at the same time it can cause problems.