so.. we stayed in a caravan on a farm about 5 years ago. the caravan was set on paving slabs that were separate to the other caravan nearby. me, my friend, my 2 kids and her daughter. my daughter and her daughter shared a twin room. I had a double bed with my young son, my friend slept in the living area.
night 1. the kids went to bed, we were up chatting in the living area. my son gets up and says, "mum, the bed is moving!" we laughed, I told him he was imagining it and I took him back to bed. then it felt like someone was walking heavily straight down the middle of the caravan. I could hear it and feel the movement but I didn't say anything and neither did my friend.
this went on for the whole week. we weren't near anything that could cause a vibration, like a train line or road.
one night I "felt" the footsteps again, my friend and I looked at each other and I said, "did you feel that?" she said "yes, I've felt it every night". it was freaky. then she asked me if I'd got up during the last night as she'd seen me in the dark, in my doorway, waving at her. she thought I was on my way back from the loo.. but I hadn't been out of bed at all. we were both horribly freaked out.
we decided to go home first thing in the morning (2 days early). I went to bed that night and muttered, "oh, do your worst!" and the wardrobe doors rattled together for about 2-3 minutes, then stopped.
so there you go. we were really freaked out but have never told the kids, and we've never spoken about it since.
I saw nothing, but certainly felt it.