How do you say I am going to sleep in Welsh?

There are a few ways to say "I am going to sleep" in Welsh, depending on the context and level of formality:

Formal:

* Rwy'n mynd i gysgu. (This is the most direct and formal translation.)

Informal:

* Dw i'n mynd i gysgu. (This is a more casual way of saying it.)

* Rwy'n cymryd cysgu. (This means "I'm taking sleep" and is a more idiomatic expression.)

More idiomatic:

* Mae'n amser i mi fynd i gysgu. (This means "It's time for me to go to sleep.")

* Rwy'n mynd i'r gwely. (This literally means "I'm going to the bed.")

Note: In Welsh, the verb "to go" is "mynd" and the verb "to sleep" is "cysgu".

The best option for you will depend on the situation and the level of formality you want to convey.