Is a retirement pension subject to Federal Income tax withholding?

Withholding is optional on regular periodic retirement pension payments. You may request withholding if you wish. Ask the payer for a withholding form.

However, pension payments (except for return of employee after-tax contributions and Roth 401k employee contributions and earnings) are taxable. You will have to pay tax on them when you file your tax return at the end of the year. And if you don't have withholding, you may have to make quarterly estimated tax payments in order to avoid an underpayment penalty.