Really hard to "time the market" - so many factors in play - both known unknowns (e.g. when will interest rates start going up again?) and unknown unkowns (e.g. errr???).
Whatever you do, there is a risk of high regret. Do nothing, market goes up, it will hurt to eventually buy at a higher level. Go full in, market goes down, it will hurt to see that paper loss (remember a gain or loss is never crystallised until you sell again).
That's why savvy investors (and academic research supports this) do something called "pound cost averaging". Let's say you want to get invested over the course of a year. Divide the amount you invest into twelve and invest (eg in a multi-asset fund) in 12 equal lumps each month.
That way you are likely to be invested at the average level for the year, rather than a particularly good or bad day. If it's a lot of money, you might want to do it over 2 years (so divide by 24).
Most DIY investment platforms allow minimum monthly "regular savings" of £50pcm, so in theory you can do pound cost average if investing £600 (£50 x 12) or more.
Pound cost averaging also means you are taking a disciplined approached to investing rather than being driven by mood/headlines which is a sure way to get hurt.