Should I do a SIP for my ELSS?
Yes.Doing a SIP in general is a good idea. By doing an SIP you can get 2 benefits.
One that you'll be able to reduce the market volatility in your investments by investing regularly and not having to time the markets.
Two you'll be able to manage your money better once the lock in period of your investments is over. Every monthly SIP you make needs to finish 3 years lock in period before you'll have the ability to remove it. Ideally you should keep your money invested in these funds to keep getting benefits but you do have the option to remove it. So instead of having to remove the money all at once and having to figure out where to invest the complete amount you'll get your access to your money in parts every month in invested order and it'll help you plan your further investments.