2003 Lincoln Navigator burning smelll

When truck is on and in operation,smells like burning rubber,and saw smoke from passenger side,gauge,never goes past hot,but is a little higher than normal,no warning lights,also when the smell starts,it becomes a little stiff and rugged when driving,mechanic first say could be hose,cause he saw moisture on and around the belt,but now saying radiator replacement,i just need a idea of possibilities,thank you.