The research on this is consistent enough to act on. Response within the first hour dramatically outperforms response the next day, and the effect is largest for enquiries where somebody is comparing providers rather than committed to you specifically. Somebody who contacted three businesses will usually engage with whoever replies first, because that reply arrives while the problem is still front of mind and the other two have not answered.
Where an immediate answer is impossible, an acknowledgement does most of the work. A short message confirming you received the enquiry and stating when you will respond properly converts silence into a known interval. The anxiety a prospect feels is about being ignored rather than about waiting, and naming a time removes it. That message can be automatic, provided it reads as though a person wrote it and gives a phone number for anything urgent.
Build the response path so speed is possible rather than relying on vigilance. Enquiries should reach you somewhere you actually look, which for most owners means a notification rather than an inbox checked twice a day. Test your own form periodically, because a broken notification produces silence that looks exactly like ignoring somebody, and the people affected do not tell you.
The quality of the first reply matters less than most people assume. A short, specific message that answers the question asked and proposes a next step outperforms a considered essay two days later. If the enquiry needs a proper answer that will take time, say that, give a time, and hold to it.
Track it if you can, even roughly. Time to first response is one of the few metrics in a small business that is entirely within your control, correlates directly with conversion, and requires no software to improve. Most businesses that lose enquiries are not losing them on price or capability. They are losing them to somebody who answered first.
Decide what happens outside working hours before it matters, since a meaningful share of enquiries arrive in the evening or at the weekend. An automatic acknowledgement stating when you will reply is adequate and honest. What damages you is silence until Monday from a business whose site implied somebody was there, because the prospect has already contacted somebody else by then.