runs great for about ten min, until it warms up

runs great for about ten min, until it warms up runs great until it warms up, then it shifts too soon. i have to turn overdrive off. rpms lowers a little. If I’m going slow like in crowded parking lot, trying to back out, it may die several times. it starts right back up and I can drive down highway without any problem except for having to turn off overdrive. But until motor warms up it runs great and I don’t have to turn overdrive off