「分からない単語を見つけたら調べてしまう癖がある」って英語でなんて言うの？

When talking about things you usually do, such as habits, you can say that you "have the habit of" doing that task. For example:

• I have the habit of using the dictionary to look up words that I don't know.
• I have the habit of brushing my teeth every day after lunch.
• I have the habit of making my bed before I leave for work in the morning.

Then again, you could always leave out the word "habit" and say:

• I usually use the dictionary to look up words I don't know.
• I usually brush my teeth every day after lunch.

If it is something that you are currently training yourself to do as a habit, you can say:

• I make it a habit to use the dictionary to look up words I don't know.
• I make it a habit to make my bed before I leave for work in the morning.

I hope this helps! ^^

1. Foible = a minor weakness or eccentricity in someone's character.
2. Little foibles = minor eccentricities
3. To have a habit of ....= to regularly do the same thing
   A: "Do you have any foibles?
   B: "Yes, I always hang out my washing very early in the morning."

"Feeling compelled" means that you have an almost uncontrollable desire to do something. It would be, in my opinion, a more natural phrasing as opposed to saying you have a habit of looking up words.

Any of these sentences can be used :-

1. I have a habit of looking up words that I don't know the meaning of .
   A habit is smoething that you practice over and over, in the same way. A habit can be good (a good habit) or bad (a bad habit.)

   2.I always find myself looking up the meanings of new words.
   The expression "I always find myself doing something " is another way of saying that thing is a habit.
   Other Examples:-
   "I always find myself washing my hands before meals."
   "I always find myself eating junk food on the weekends."

When you want to explain that you have a habit of looking up words that you do not understand, then you may explain this in the following ways:
-I habitually look up words I don't understand
-I usually look up words that I don't understand

To explain that you have a habit of doing something, in this case looking up words that you don't understand, you can say:
"I have a habit of looking up words that I don't understand."