Is it normal to always be shy and nervous in public?

yep thats me

I think you might have social anxiety disorder(a.k.a. social phobia). And you certainly are not the only one. Many people have this disorder, but the good news is that, you probably are in the early enough stages to probably overcome it through treatment. Maybe a psychologist could help you.
I get it sometimes too. I think its because a lot of times Im spending too much of my time worried about what other people think. Maybe youre like that too?

Normal. Im one of the shysters. What helps my anxiety is that i listen to binaural beats and meditate for a while. Or get plastered before interacting with society. The latter is not recommended. You could try downloading social anxiety help torrents. I did but I have yet to listen to them, for they might cast a spell on my awesome and make me boring like the rest of them.

Problems inside the mind are always slippery. Like trying to grasp smoke in your hands.

Confide in someone. I used to have a fear of driving and I kept it for 3 years. It wasn't until I told my mentor about it and she revealed how stupid it was that I finally beat it. But most of all: don't give up. No matter how many times I failed at beating my fear it never deterred and I eventually won.

People like to preach that psychiatry isn't the answer. Those people are wrong. It does sound like social anxiety, and benzodiazepenes (Ativan, Klonopin, etc) work wonders. No side effects, no messing with your head, no waiting weeks for them to work. Just pop one (or five) and in 2-20 minutes (depending on the drug) a huge portion of your anxiety will be gone. This'll get you functioning, and able to get experience and maybe therapy that'll lessen or eliminate your need for medication over time. An interesting effect of benzos is that even when shaking hands aren't caused by nervousness they still treat that symptom. Drugs that mess with the kidneys (Lithium, some breathing treatments, etc) tend to cause hand tremors and benzos are quite helpful at combating that.

Another option, one psychiatrists tend to be more fond of, is using an antidepressant with anxiolytic properties. A good portion of these belong to the tetracyclic class of drugs. They can be pretty effective but they take weeks to build up in your system before they'll work, and it's nowhere near guaranteed that they'll work at all, unlike benzos. Another downside is that you have to keep the levels up in your system, meaning you'll have to take the drug regularly, as opposed to benzos which you can take as needed. Really the only reason doctors like going this way is because benzos can be used recreationally.

What are you so insecure about? Find that answer and work from there.