My 3 Year Old Toddler Has Episodes Where She Stops

My 3 year old Toddler has episodes where she stops whatever she is doing and seems to go into a state of being unaware of anything around her. She will stop playing, watching a program, dancing...I have gotten in her face and tried to get a response from her and got nothing. Sometimes this will last a few seconds and often a minute or two. Do I need to have her checked and by what kind of Dr?