I think a larger issue is that you're trying to do market timing. Whether you had a large or small amount of money to invest, no one wants to put the money in to watch it go down.
You can't really predict if prices in a market or security will go up in six months (in which case you want to put all your cash in now), of if it will go down (in which case you'd want to wait until the bottom), or if it will skitter around (in which case you'd want to only buy at the bottoms).
Of course, if you're magic enough to nail all of those market conditions, you're a master finance trader and will quickly make billions.
If you're really concerned with protecting your money and want to take some long positions, I'd look into some put options. You'll of course pay the fees for those put options, but they'll protect your downside.
Much of this depends on your time horizon: at the age of 35, someone can expect to see ~6 more recessions and perhaps ~30 more market corrections before retirement. With that big of a time range, it's best to avoid micro-optimizing since that tends to hurt your performance overall (because you won't be able to time the market correctly most of the time).
One thing that's somewhat reasonable, if you have the stomach for it, is to not buy at somewhat-obvious market highs and wait for corrections. This isn't fool proof by any means, but as an example many people realized that US equities basically were on a ~5 year up run by December 2014. Many people cashed out those positions, expecting that a correction would be due. And around late summer of 2015, that correction came. For those with patience, they made ~15% with a few mouse clicks.
Of course many others would have been waiting for that correction since 2010 and missed out on the market increases.
- Market timing can work, but it's notoriously hard to do correctly. The market has made a lot of people broke who were trying to time it.
- Put options can work to limit your downside. They make sense primarily in shorter time horizons (weeks/months).
- The longer your time horizon, the less you really need to worry about 300 point up/down swings in the DJIA.