Thanks for explaining it so clearly. I’ll answer the way I would in clinic.
A pounding or “throbbing” heartbeat after starting Vinicor-D is not something I’d ignore, especially since it’s waking you from sleep.
Vinicor-D commonly contains metoprolol + chlorthalidone (a beta blocker plus a diuretic). 
A few possibilities come to mind:
1. Low potassium / dehydration from chlorthalidone
* This is actually a common reason for palpitations / pounding heartbeat, often more noticeable in the evening or at night.
* You may also notice:
* weakness
* muscle cramps
* dry mouth
* extra thirst
* feeling “off” or anxious
2. Blood pressure dropping too much
* Can feel like pounding in the chest, dizziness, fatigue.
3. Heart rhythm irritation / ectopic beats
* Sometimes you feel every beat strongly even if the rate isn’t very fast.
4. An unrelated issue uncovered after starting treatment
* anemia,
thyroid, anxiety/stress, caffeine, dehydration, etc.
My medical opinion:
Because:
* you’re 29
* symptoms started after beginning the medicine
* it’s persistent
* and it’s disturbing sleep
…I would contact the prescribing doctor within 24–48 hours and ask for review.
That review may include:
* BP readings (morning/evening)
* Pulse
* ECG
*
Electrolytes (especially potassium/sodium)
*
kidney function
Important:
Please don’t stop the medicine suddenly on your own tonight unless a doctor specifically told you to—beta blockers are usually better adjusted deliberately.
Seek urgent care tonight / immediately if:
* chest pain
* fainting / near fainting
* shortness of breath
* pulse racing continuously
* severe dizziness
* BP very low
* irregular heartbeat that won’t settle
A couple of quick questions so I can guide you better:
* What dose exactly is it—25 mg or 50 mg?
* What’s your BP and pulse lately?
* When the pounding happens: is the heart fast, irregular, or mainly strong/heavy beats?