I always do this. Whenever someone is talking, I always impulsively interrupt to ask questions (if I feel an important detail is missing) or to add a comment (to make me seem engaged in what they're saying).
Most people talk fairly slowly with pauses which often makes me wrongly assume they've finished talking and I come across very intense and rude.
Another reason is that I am almost terrified that they'll get to the end of what they want to say and I won't have prepared what I want to say back so I start prepping my response in my head whilst they're talking and then worry I'll forget my response so just blurt it out before they're done talking. I am a very erratic, "quick" person (i.e. extremely quick in walking, speaking, thinking, typing, running) as my concept of time is very distorted - a 2 second pause feels like a minute silence to me.
Any advice? I'm glad I'm conscious of it at least but still finding it soo hard to not to do it due to the reasons above!