Welcome to the forum.
Suddenly feeling jittery, chest tightness
, light headedness without any cardiac or lung disorder, with no history of smoking, alcohol or drugs points towards anxiety
To help this problem you can take a few measures-
1.Check your caffeine intake-Avoid drinking too much tea, coffee or cola.
2.Avoid alcohol and cigarette smoking
3.Try physical exercise like aerobic exercises daily for twenty minutes.
4.Avoid your worries and problems or solve them with the help of your family and friends.
5. Learn controlled breathing.
6. Do simple relaxation exercises like yoga
You can also discuss the problem with your GP who will help you in choosing a good antianxiety drug with low day time sedation.
I hope this is helpful to you.