What actually starts labor 🤔🤔

Taylor 💍 • Jeremiah 29:11 🙏🏾I stand on the

So I’m laying here in bed wondering what actually triggers labor to start ... like is their a chemical released in our body that says it’s go time or what ? I can’t seem to find a clear answer and I’m trying to see what signs to look for as I’m nearing that time(I’m 35 weeks)