PigBoat, most likely something inside the plane is touching something it shouldn't. Check all your wiring and servo cables as well as antenna and make sure they are where they belong, also look at the motor wires and make sure all the connections are good. If it's glitching before you turn on the TX then something is not right in there. I have had planes that glitch after in the air and it will and has caused crashes, think about it like this your dropping in for a low fly by or even a landing and then it starts glitching and kicking your rudder or even elevon, now your risking a stall, fortunatly the T-Hawk is so easy to fly so control is probably possible, but I would try to find and fix it
Good luck with it