I always feel sleepy after a meal and sometimes actually doze off mainly if I eat at home..Can somebody explain this or maybe I have an underlying health issue I don’t know about?

It is normal but if it happens too often or even after a light meal, then go for check up.

Mine only happens after a very heavy meal like beans and yam, pounded yam or fufu with better vegetable soup and enough obstacles.

Check your blood sugar.

after meal you are supposed to use the energy derived from the food productively. if not, you will sleep. next time at eating try and get engaged in some activities apart from sleeping