What could cause Lightheadedness, tightness in throat along with palpitations and brief chest pain? Sometimes low resting heart rate of 45-60 BPM.

Emergency room . You should see a cardiologist but meanwhile try to reduce caffeine intake Stop smoking if you do Try to decrease any factors that lead to anxiety .
Need context. . Your symptoms are curious, but I would need more information about clinical context. If these symptoms are occurring with activity, I would think of the heart. If they were happening after a meal, I might think of reflux. If they're happening at rest, I might even think of anxiety. Clinical context is important. But regardless, these symptoms should be investigated. .
Good afternoon. There are many causes of these symptoms which cannot be expanded on in 400 character, but if this happens often to you then I would advise seeing a physician for an EKG and possibly an event monitor if there is concern for arrhythmia. Basic blood work should be check, particularly the thyroid. Point being it would be impossible to know without obtaining further history and testing.