Diagnosis
This is a common quirk with the mechanical thermostat in these models. It's not a digital precision device. The "constant" cycling is its normal operation to maintain an *average* temperature, but it can be overly sensitive.
How to Fix It
1) Try turning the thermostat dial (the outer ring) to a much higher setting. If you want a 70°F room, set it to 80°F. This gives it a wider buffer and reduces cycling. 2) Make sure the heater isn't placed right next to the thermostat dial or in a drafty spot like under a window. The heater's own heat or a cold draft can trick its internal sensor.
If That Didn't Work
The thermostat mechanism itself might be faulty or dirty internally, causing erratic contact. This isn't a user-serviceable part.
Heads Up
Short cycling (on for 30 seconds, off for 30 seconds) is somewhat normal. Long cycles (on for several minutes, off for several minutes) are better. If it's rapid-fire clicking every 10 seconds, that's excessive and points to a potential fault.