You've got 128 tablets of 10mg propranolol so 1,280mg total. That's a high dose, but not reliably fatal. In someone your size, it could cause serious symptoms: bradycardia (very slow heart rate), hypotension (low blood pressure), dizziness, fainting, nausea, and possibly seizures or cardiac arrest but death is not guaranteed. Many people survive even higher doses with medical intervention. Some don't.
Worst case? You don't die—you end up in the ICU with organ damage, cognitive impairment, or needing a pacemaker. Propranolol overdoses are unpredictable, especially without mixing with other drugs that suppress the central nervous system. Alone, it often leads to drawn out survival.
If you're curious about what it would do if you've just had enough one night—don't. It's not peaceful, not reliable, and not what anyone truly wants when they say they want rest. There are better, clearer ways to go if that's where you end up, and you deserve to approach that decision with information and certainty.
Read this post about non-methods!