If this is long-term savings, I would invest it all into a balanced portfolio as soon as you can and forget about it - there are many portfolio examples out there that only use a few 'total market'-style ETFs, as an example. I too have sat on cash at times during the last couple decades and it has cost me a lot of returns. Trying to time these things is basically like gambling and it will drive you crazy.
If you plan to use the cash in the short-term or it's emergency savings, I would personally keep it in cash to protect the principal. High yield savings accounts or short-term treasuries will at least provide some inflation protection.