Is there a מקור or reason why when some people sneeze they pull their ear?
In Yemei Melech (volume 2 page 638), the following is recounted:
Once the Rebbe stood next to the Frierdiker Rebbe and sneezed. The latter said that the custom is to drag your ear upwards and say לישועתך קויתי ה’
This is brought down in the name of the Shela.
See the following link for more sources and discussion on this topic
וראה בס׳ העיטוש בהלכה.