3 year old keep being sick

hi everyone, i have a 3 year old little girl. Every 2-3 months she is being sick in the mornings only, the day before she is sick she refuses food and drinks. She has no temp no rashes. She does become very sleepy though i have spoken to doc who always seems to say its viral. I just wondered of any other mum have experienced this, like i said its happeninh every 2-3 months thanks