スタバに行ってコーヒーを飲みながらぼーっとするのが好き！って英語でなんて言うの？

When you are doing something 'over a coffee' this means that you are doing it whilst having a coffee. This can be used in other ways too, for example - "We had the meeting over tea and biscuits."

In both sentences you are expressing the idea that you want to go to Starbucks, have some coffee and daydream. Notice that I added "sit back and relax" in the first answer, since in order to "daydream", you would have to sit back and be in a relaxed atmosphere for your mind to wander off and starts to daydream. It adds the scenery and create an image in the listener's mind and makes the response more natural and applicable.

You like going to Starbucks and daydreaming/zoning out while drinking coffee. You can explain that as indicated in the example above.

When you do something whilst drinking a cup of coffee, it indicates that you are looking deeper into your heart because of something that you need to make a decision over or because you have certain feelings for what you daydream of. This sometimes can be related to you being happy or just wanting to explore your emotions to what you are feeling or doing. If you like to zone out because of decisions you are about to make or making, you tend to go over your decision before you make it or go over your decision after you have already made it and it makes you feel good.

Zone out', 'space out' or 'let your mind wander' all mean that you don't think of any particular thing - you allow your brain to think of whatever it wants: you are not consciously thinking or focused but you just allow various thoughts to flit across your mind. To say "it's great" means that you really enjoy or like something.

When you want to explain that you like going to Starbucks and zoning out while drinking coffee; then you may express this in the following ways: -I like going to Starbucks and getting lost in my thoughts while I have my coffee. -I like going to Starbucks and daydreaming while I have my coffee.