It feels like my speaking ability comes in waves. Sometimes the words don't come to me, but some other times they do.
この場合、次のような言い方ができますよ。
ーIt feels like my speaking ability comes in waves. Sometimes the words don't come to me, but some other times they do.
「私のスピーキング力には波があるようだ。言葉が出てくる時もあれば、出てこない時もある」
to come in waves で「波がある」と言えます。
words don't come to me「言葉が出てこない」
words come to me「言葉が出てくる」
ご参考まで！
"It comes in waves, and lately the words just don't come out."
"It comes in waves, and lately the words just don't come out."
"it comes in waves" 「波でくる」・「波があって」
"lately"「最近」
"the words just don't come out" 「全然言葉が出てきません」
[波](https://eikaiwa.dmm.com/uknow/questions/28702/)についてもっと詳しく知りたい方はクリックしてください。
カナダ 
オーストラリア 
