Does the sparking plug have a sensor? - Bosch 1600H-NG Natural Gas AquaStar AquaStar Natural Gas Tankless Water Heater...

Check pilot is clean and strong Also check sensor is clean and connections are clean and tight .

Change the heat sensor.

The igniter may not be receiving the call for heat, im not familiar with these setups, but if there is sensor or a heating element they could have gone bad.

Clean plug connection on control board ,if no luck change board.

This is either a problem with the spark igniter or the circuit board. Here is a link to all of the spark electrodes for Suburban:
http://suburbanrvparts.com/furnace-parts/furnace-parts-by-category/spark-electrodes/
Here's a link to the circuit boards for Suburban furnaces:
http://suburbanrvparts.com/furnace-parts/furnace-parts-by-category/module-boards/

in front

Is there an internal sensor in the tank that tells the thermostat to call for heat. It wont call for heat until manually turned on the thermostat

it sounds like the flame sensor is dirty or faulty. when the pilot lights the flame sensor rod recognises the flame to allow the main gas valve to open and ignite the burners. you can clean the flame sensor with some steel wool or sandcloth

If the water heater shuts off again unplug the white the sensor plug underneath the thermostat (The black plastic box). Then plug it back in. This sensor plug has a black and white wire going to it and it's possible the plug could have been loose going into the thermostat..
If the problem persists you will need to contact the manufacturer at 1-877-817-6750 and they can assist you.

You won't see any red glow until the burner ignites and burns for a while. Its only an ignitor and flame sensor, not a glow plug style.The ignitor has to provide spark for gas to ignite, then it also senses the flame and keeps gas flow coming. What exactly is happening when you turn it to on?