I'm pretty risk averse, so I would be pretty cautious about borrowing money to invest.

Do you have a job lined up that you will be using to make the payments, or are you planning to pay it back out of the money invested?

If you need the loan proceeds to pay off the loan, you could still do something pretty conservative with the money like a treasuries ladder (if in the US) and just pay it off if the yields on those ever go below the 3% interest you are paying. Assuming you can do an early repayment with no penalty.

If you don't and are confident you can make more than 3% on the money over the course of the 5 years, and can just leave the money invested for the long-term, so you're just kick-starting your investing with this money, then that's less concerning. But if you're using income to pay back this loan that you should be putting in an emergency fund or investing in retirement savings etc., I wouldn't.