My 4 year old has had a fever of 100-103 since last night & a cough,plugged nose & wants to sleep all day. when should i take her to the hospital?

Viral infection: Nasal congestion, cough and fever are pretty classic for a viral infection like influenza and can be treated symptomatically with fever meds unless there is a problem with breathing in the chest or your child has a history of asthma or pnemonia or immune disorder. If fever lasts more than 4 days, or resolves and then returns after a few days, then a secondary bacteria infection is likely & see MD

Pediatrician better: Your first choice should always be your regular provider, whether that is a family physician, nurse practitioner or pediatirician. They have your full history and know the case. Colds are self-limited, and fevers in that range are common for children that age. ER's are expensive and you usually have to wait for many hours. A temp>104, stiff neck, difficulty waking child up, ER is reasonable.