How to re-gain energy when too exhausted to talk?

I've had this problem for years but it got worse recently. Sometimes i just get so exhausted talking seems like an impossible task, but i have to talk, theres no way to tell someone that im not talking because im way too tired. No idea what causes/triggers it and no idea how to gain back the energy to talk. Its a major problem and its disturbing my everyday interactions and ability to do things in school