Wow blondie, that must have been scary. Here are some questions that can help you decide whether you think you had a seizure or not: Did you black out, were you confused, did you go deaf, did you have an out of body experience, did your vision go? Did your heart race, did you stiffen, did you drool, did you sweat, did you make sounds? There are MANY more questions but those are the basics. Most people say they feel "strange" right before they have a seizure... did you?
Gosh I really hope you didn't have a seizure. Does anyone in your family have Epilepsy? If you are genuinely concerned about this you should see a doc.
I know that when I don't feel good, durning a bad IBS attack or when I get sick (puking), I shake. Anytime I don't feel good I shake. I don't know why but it happens. I used to scare the crap out of my man; he felt so helpless. After a little while it would just go away. Never by just standing up though.