2018 W-2 shows combined withholding of $629.16 (state and federal). Total withholding on all paychecks shows combined withholding of $2628.55.
Is the rest Social Security and Medicare payroll taxes? If not, talk you your employer.
The difference is just about $2000. That might be a 401(k) or similar plan, health insurance premium, or something other than taxes withheld.