2000 toyota sienna runs rough,cooling fan always on

my 2000 sienna cooling fan always on,rans rough need help

If the A/C switch is on, or defrost is on, the radiator fan is supposed to be on. Check those switch positions.
When the engine is cool, open the radiator cap and add anti-freeze, if it has space. If the radiator is down, a mechanic needs to find out WHY.
Get a mechanic to check the engine heat. If the engine is at normal temperature, the radiator fan relay could be stuck, the engine coolant temperature sensor may be faulty, there may be wiring problems.

How many miles on this vehicle, and is all maintenance up to date? Is the check engine light on?