We experienced this with Oz, my youngest, when he was about 4 months old. He looked very similar to Jaspar in that he kept trying to get up but couldn't. He was also very aware of what was going on at the time so I know it wasn't a seizure. Like Jaspar, he recovered very soon and acted like nothing had happened. He has not had an episode since that young age. Sometimes I believe they grow out of it (as Oz did), sometimes it stays with them. I took him to my neurologist since I already had a relationship with one as I have a dog with SM. He examined him - no neurological deficits and said to just watch him.
Since Jaspar is having 2-3 a week, I would definitely go to the link Margaret suggested and try to get in contact with someone who can give you better medical information about what you should be doing. Good luck.