You can use a Formula to automatically convert a field’s text to sentence case.
For example, you can set text to sentence case in the "Description" field of the "Customer" sheet.
Create a new field and apply this formula:
TOUPPERCASE(LEFT(A8, 1)) + TOLOWERCASE(RIGHT(A8, LEN(A8) - 1))
Replace A8 with the field you want to reference.
This will automatically capitalize the first letter of the sentence.