Transmission works fine till fluid gets warm then acts like it locks up and won't work

Hello, 1999 Accord automatic transmissions are not really known for problems. However, you could certainly have a ton of miles and some unspoken history for the vehicle. Check for any diagnostic trouble codes. If you have none showing, then yes - it's likely an internal transmission concern. Replacement is likely needed. If you show codes, testing will be needed to drill down to the cause. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.