Start of Contractions?

I am just over 36 weeks along. My doc just checked the baby, he was head down so close that she could easily feel him with her fingers. I wasn't dilated or anything yet. However last night o had a lot of Braxton hicks contractions. And today I had them accompanied with short brief shocks of pressure/pain very low in my lady bits. I never hear you experienced moms talk about what contractions feel like when they first start, or how long they are? I would love to learn a bit more from your experience. Thank you ☺️