It can be in any number of places... if you can provide a model number, perhaps I can check for your unit.
I have found them:
Inside the kick plate area below the door
Behind the temperature control in the cooler side
On the rear of the cabinet when there is a control board
When you say it's "freezes," does that mean the coil is frosting/icing up and blocking the air flow? If instead, you mean the product in the cooler side is freezing, this timer has nothing to do with that.
They're very easy to replace... 2 screws and a 4-cond. electrical plug. The common one can be had for under $10... You can order one through Walmart with free delivery to the store.