Thermostats open and close a lot is it possible that a thermostat malfunctions and stays in closed position overheating the engine?
I bought an aftermarket MotoRad thermostat I am wondering If I should've bought an original from Jaguar

 

A thermostat sticking shut is always a possibility. You can do a simple check and pull the thermostat from the car. You can then put it inside a pan of hot water and heat it up some more. You should see the thermostat start to open at probably around 180-185 and be full open at the set temperature of 195.

During normal driving, the thermostat does not necessarily go full closed and back to full open to maintain temp. It really drifts towards closed and towards open, restricting flow as necessary to force the needed amount of water through the radiator to maintain the temp. If you have a random overheat, then I would say to look at the thermostat. But, if it is fairly consistent, then I would be looking elsewhere since you have a newer thermostat from the sounds of it. Normally a thermostat will get some gunk on it and stick every now and then or it will start drifting in where it will maintain temp (ie, over the course of a few months, start controlling higher and higher until you get the periodic overheat from after say coming off of the highway, but it would only last for a few minutes, then it will return to normal).