This ticking occurs when the heater element expands and contracts due to the heat it produces. The heater element rubs against the brackets that are holding it in place. It also may be rubbing against the holes it is mounted in. Try this.
Turn heater off. Remove the cover and heat shield from the baseboard. Use Scotchbright or other similar material to clean and smooth the heater element in areas near the brackets and mounting holes. Use a VERY SMALL amount of white lithium grease on the heater element near the brackets and mounting holes. Turn on heater. Caution - when the heater turns on you may get some smoking for a short while, this is due to some of the grease burning off, leave room adequately ventilated, stay with heater until smoking stops, if flames occur simply pat out. Some of the grease might not burn of and this may solve your problems, it did for me.