starting problems ?

I have a CARDIO TRAINER 600 treadmill over a year now which i hardly use. I plugged in the unit and it doesn't start up after about 3mins it starts up by it self without the safety key in the slot .the speed goes up and the incline only move up 1 level and the unit doesn't stop when you remove the safe key or press stop. the unit will only stop when you unplug or turnoff the main on/off switch