You can warm your baby's formula if you would like, but try to make it easy for yourself. Room temperature formula is safe for your baby and easy for you.
If you do choose to warm the formula, never use the microwave and always check the temperature on your own skin first. You can get uneven heating with microwave ovens. This is dangerous as you may check the formula temperature before giving it to your baby and it seems fine. Unfortunately, there may be very hot liquid another level down.