I think i know what it is. If your new to wilding then your heartbeat is always going to increase since your scared of whats going on. Oh i hear things, or oh this is different. Your going to feel different things. Your heartbeat is unliklely to go incredibly fast, but it will speed up. It has for me the last 10 times ive tried wilding. So just relax. Don't focus too much and just relax.