The crowded train carriage is rocking rhythmically. It might be accidental and you don’t want to come off like a screaming hysteric, but still. That leg, arm or pelvis pressed against you is uncomfortable and you’d rather it wasn’t there. Like when Mark from Peep Show put his hand on the bus seat and then Soph sat on it. He probably doesn’t even know and will be mortified if you were to call him out publicly. He looks alright. Not weird or anything.
Phew. You shifted and the contact is broken. That could have been really awkward.