I am in my Mid 20’s & have $210k in cash sitting in the bank account, I feel very stressed everyday as I know I’m not making full use of the money to invest and grow my bank account. Any advice?

Congratulations for saving so much money in your mid 20s.

I'm older and I earn about half of what you earn. Shiaks, now I'm stressed... 🤣Anyway, since you're pretty new to investing and you want to grow your money at a stable pace of 4%, you can consider CPF-SA. Of course, you don't see them until decades later.
How to Get $1 Million at 65 Using Your CPF

https://blog.seedly.sg/1m65-1-million-by-65-cpf/
If you don't wish to place with SA which is kind of risk-free (I say "kind of" b'cos nothing is really risk-free, even still backed by govt. but more like it's lower risk than what's out there), then you must know that to get 4-5% elsewhere, you need to own equitities and these don't come risk-free.

Whether it's ETF bought via stock brokerages (like FSMOne RSP) / robo-advisors or funds, all are in stocks. Only difference is your amount of portfolio exposure to the stocks part.

With minimal effort, robo-advisors are a better consideration, than if you DIY for ETFs via stock brokerages. You can read the difference here: https://seedly.sg/questions/are-roboadvisors-go...

Currently, I'm with Endowus for my CPF-OA investment. So far, stress-free for me, 'cos I can't get the monies until I retire. 😂 Out of sight, out of mind. I gave my input about them in this reply: https://seedly.sg/questions/i-have-20k-savings-...

You can try with your cash. Do make sure you spread among the robo-advisors to diversify your risk.

All the best, chillax, and enjoy your youth! 😁