once in a while

I write a letter to my friend.

私は友達に手紙を書きます

I write a long letter to my friend.

私は友達に長い手紙を書きます

I write a long letter to my friend in a quiet room.

私は静かな部屋で友達に長い手紙を書きます

I write a long letter to my friend in a quiet room at night.

私は夜に静かな部屋で友達に長い手紙を書きます

I write a long letter to my friend in a quiet room at night once in a while.

私は時たま夜に静かな部屋で友達に長い手紙を書きます