I can think of 3 times that I absolutely lost it for no reason:
1) During the movie Ever After...the scene where the old people are running towards each other in the field..o..m..g.
2) A mosquito flew too close to my head and I LOST MY MIND...sobbed for a good 10 minutes.
3) Nic made a funny gesture behind the doctors back at like my 30 week appointment..and I started laughing..and then started bawling lol
Im sure there were more..so..yes, frequently