Not sleeping through night. Sleep about 4 hours, rest of night half awake. Resting heart rate 103. Thyroid?

Could be. Hi. That could be thyroid, and it's very easy to check. Talk with your doctor. Good luck!
Possibly. There are many conditions that can elevate resting heart rate and interfere with sleep, from benign to concerning. Please see your primary care provider to get evaluated to identify cause and treatment.