I have a 2001 Ford Mustang, v6 3.8 5 speed manual

Hi Bobby, I found this bulletin on I believe the problem you are talking about. Hopes this helps ya put.. Cobra.. Please read..
FORD: 1999-2004 Mustang
ISSUE: Some 1999-2004 Mustang vehicles equipped with a T5, T45 or TR3650 manual transmission, may exhibit a hard to shift condition into first or reverse gears from a stop. This may be due to an incomplete disengagement of the clutch (lack of clutch pedal reserve).
ACTION: Refer to the following Service Procedure. It may be necessary to adjust the clutch pedal down-stop and the clutch pedal shaft nut to gain full pedal travel.
SERVICE PROCEDURE

1. Lift up on the clutch pedal to reset it.
2. Measure the clutch reserve per the instructions listed in the Workshop Manual Section 308-00, Diagnosis and Testing, Manual Transmission and Clutch. NOTE: THE MINIMUM RESERVE NEEDED FOR GT, LX AND 1999-2001 COBRA IS 19 MM (3/4").
   
   
   1. If the measurement obtained is larger than these values, DO NOT CONTINUE WITH THIS TSB. Follow normal Workshop Manual diagnostics listed in Section 308-03.
   2. If the measurement obtained is less than these values, make sure that the floor mat or excessive material under the carpet is not preventing the pedal from reaching its full travel. Correct any obstruction, if the condition is corrected return the vehicle to the customer. If the condition is not corrected proceed to Step 3.
3. Visually examine the pedal down-stop to see if it is preventing the pedal from reaching its full travel to the carpet. Correct if necessary by removing the rubber pad on the down-stop. If the condition is corrected return the vehicle to the customer. If the condition is not corrected proceed to Step 4.
4. Additional travel can be obtained by loosening the clutch pedal shaft nut and adjusting as needed per Section 308-00 of the Workshop Manual. If the condition is corrected return the vehicle to the customer. If the condition is not corrected proceed to Step 5.
5. If inadequate reserve is still present refer to Workshop Manual Section 308-00 for clutch pressure plate and disc diagnostics

The clutch is not fully releasing. You can try putting it into some other gear first, then rapidly moving to first gear, but really, you need to either adjust the clutch, or get it repaired.