Other tests which may help are round the clock sugar monitoring, holter to rule out arrhythmia and situational
hypotension/hypertension, blood tests
for electrolytes, vitamin B12, vitamin D and hyperparathyroidism.
Some sleep disturbances can also make you feel jittery during the day. So, it may be worthwhile to undergo sleep studies if no other cause is found.
Please discuss with your doctor. Take care!