Questions: To begin investing or continue saving? Advice?

Hello

I am 23 years old and debt free, thankfully! I have a 10K Emergency Fund saved as cashiers checks and a 7K Saving/Sinking Fund, a part of it is in a savings account the other is in cash. The company I work for offers Simple IRA, and I signed up, but have yet to put it to work. I finished the course and like the simplicity of a target date index fund. What do I do if there isn’t a target date index fund with my year?

My career plan is to apply to medical school in two years, and I know this means debt to come. This brings me to my next question, if I should hold off on investing on a different account through fidelity (not the SIMPLE IRA) and continue saving? Or begin investing?

Any advice, or suggestions will be appreciated,

Thank you!