Is it normal for my 4.5 year old to have fever 3-4 times a year. especially in the colder months?

Fever: Many children develop minor illnesses that produce low grade fevers, and even trauma or overactivities can raise the body temperature. Would need to know a lot more about your little guy's symptoms and whether he is in day care or pre-kindergarden, etc. What you describe is not unusual, but if concerned have him seen and assessed by a local pediatrician. Best wishes.