When in a minecart, the enderman tries to teleport several times, even without being hit by a projectile or damaged by water or rain. It seems to only happen when it's under daylight.
How to reproduce:
1. Set time to day:
/time set day
2. Summon an enderman riding a minecart:
/summon minecraft:minecart ~ ~ ~ {Passengers:[{id:"minecraft:enderman"}]}
3. Close to the ground, wait and listen.
[media]
Can confirm.