It could be night terrors? I think you'd need a GP diahnosis for that as Naomi suggest.

My son , whos almost 14 months, has starting waking more an night, screaming - not necessarily crying - and does the throwing his body around as well, but he does it in my arms not just in bed. Once I calm him down he is usually OK to go back to sleep though.

With the teething issue - I also thought that if it was teething pain Milo would still be upset when I picked him up etc, but for him it doesn't necessarily work that way - its more that when there are no distractions and his body can relax, he noticed the pain more than when someone is there or theres something else to do.