I’ve been pondering the mysteries of the Bitcoin market lately and I just had to ask—how do we know when retail investors are FOMO-ing into Bitcoin?

You can look at Google trend and some indicators for Bitcoin bubble that bases on Google trend and some stats from social media platforms.
https://trends.google.com/trends/explore?date=all&q=bitcoin&hl=en
https://www.coinglass.com/pro/i/bitcoinBubble
https://www.theblock.co/data/alternative-crypto-metrics/web-traffic

You can look at Bitcoin heatmap that is given by Glassnode in their report like this one
https://insights.glassnode.com/the-week-onchain-week-18-2024/

You can simply see what's happening around you. If many people around you start to talk too much about Bitcoin, this market while just previous months, they did not care about it, it's good signal that retail investors are coming.

Thanks mate. I did not know about theblock.co. That looks like up to date website to keep an eye on.