I didn't start feeling mine until 27 weeks or so. They were very noticeable to me afteri felt a pattern in movement. My son also very obviously hates them. He moves like crazy when he gets them now.
it feels like a steady kick to me but does come back to back like a heartbeat or a pulse. My son gets them all the time.. sometimes they last so long (5-7 minutes) I get annoyed haha & they are very noticeable to me but I am 33 weeks.
They feel like a heartbeat :) my son has them so many times during the day. I love it lol