Transaction fees can skyrocket anytime due to those garbage that are using bitcoin network but this not often and that is why whoever is DCAing should consider high transaction fees in future so that you don't end up using your profits in the long run to pay for high transaction fee.
This is why it is good that if you are DCAing when the transaction fee is very low just the way it is currently, you can consolidate y our small inputs into a big output for the future. You should make sure that the smallest input should be from $500 and above in one transaction to enable spend little fee in future.
On the other hand, if you are DCAing and the transaction fee become high, you can pile up your weekly DCA or monthly in your exchange account till it gets up to $500 and above excluding your transaction fee before sending it to your noncustodial wallet. Or you can leave it in the exchange till the fees goes back to normal, it is your choice. But save your bitcoin investment from high transaction fee depreciating too much of your profits in future.
I have experienced such a situation, and there is no problem with leaving it on the exchange for a while. because indeed high fees will be very burdensome for Bitcoin investors with DCA. there is still a risk but it will not be that high. moreover, if the situation of high transaction fees does not occur for a very long time, the situation will improve.
after that experience, I prefer not to make a purchase first when the situation is like that. temporarily saving the allocation will be more comfortable for me. but still saving funds to be ready to spend when the situation improves.
Bitcoin transaction fees don't always rise up, if it is rise up it will not last long. Fees increase for very short time but I think it is not a big problem for investors. Temporarily DCA holders may worried due to high transaction fees of Bitcoin. But the biggest loss at that time is those who are small investors. What we can do to solve this issue is to temporarily hold our funds on a centralized exchanges so that they can be re-transferred when the transaction fees come down.