Rheem Gas Furnace Intermitant Blower Running

[Normstorm]

Rheem RGTK09EZAJS Gas Furnace. Blower fan has turned on in middle of night even though T Stat set to "Auto". The first time I woke up to fan running non-stop and the "Cool/Off/Heat" on T Stat was set to "Off". The next two times it did same thing with T Stat in "Heat" position.
Heating cycle worked normal a couple of times each morning and the Blower turned off appx. 2 minutes after burners shot off. Only have had furnace on a few times in AM since afternoon is not needed yet due to mild temps outside.
Any ideas why this happens or what things to check first?  This model has a Circuit Board control and is a 2006 model year.
Thanks for any help.

[beaconservices]

I am wondering if you ever found the solution for this. First, that model has a PSC motor so that rules out a ECM module doing things it shouldn't. You could have compromised control wiring, with the G terminal wire coming in contact with voltage. I can't imagine a blower board just randomly engaging it's blower relay without being told to.

[VTP99]

Some furnaces will run the blower after a high limit fault in heat mode. I didn't look up your model is there a diagnostics light on the control board ?