If in IDLE you see something like
>>> import pandas
================================ RESTART: Shell ================================
>>>
and no traceback such as
Traceback (most recent call last):
File "<pyshell#21>", line 1, in <module>
import pandas
ModuleNotFoundError: No module named 'pandas'
or one with another error, then almost certainly something called pandas or pandas.py was found on sys.path and execution was attempted with the result that the python subprocess doing the execution crashed. Perhaps you have a file called pandas.py in your current directory, or perhaps the installed pandas file has a messed-up byte.