Mysa turning your heaters on and off frequently is the intended behavior. Mysa's control algorithms will quickly turn on/off the heater to stabilize the room temperature, which will help you feel more comfortable and save you money. The picture below is a graph representing a room heated using Mysa's control strategy.
Manual thermostats usually use ON/OFF control to heat your room. ON/OFF control means that the heater turns up to full power, reaches it's temperature, then shuts off. When it senses that the room has dipped below the setpoint, it repeats this process. Using full power and being reliant on temperature falling below the set point means two things for the average user: it uses more energy than necessary, and it fluctuates from the setpoint by as much as a few degrees at a time. With no feedback control, this means that it will often rocket past the setpoint, giving you an uncomfortable heating experience.
Tip: Some customers with fan forced heaters want the fan to cycle less frequently. To do so, select a longer cycle time in the Mysa app. Read more about cycle times here.