Your motor is the 1400cc turbo
Obvious 1st question...
Has the coolant level remained stable?
Losing coolant slowly is not unheard of.. Then you have restricted cooling capacity
If your coolant level is still good.. Then yes it's worthwhile changing the thermostat.
With the simpler non. Turbo 500 we see in Europe the assembly is inexpensive... So they tend to get changed regularly
The Turbo diesels have a complex thermostat assembly..
Read 'expensive' ..!
Around 10 times the price means they get left alone..
This forum had just updated it's link to the Fiat parts system.(
ePER)
So modern era cars are now included..
Have a look to see if your Multiair motor has a Service Kit for it's thermostat
Do let us know what you find..