I have also experienced this, but only with nicotine gum by chewing the heck out of two 4 mg pieces in rapid succession. I can vape 33 mg juice continuously and not get hiccups. I suspect that you have a low nicotine tolerance, which is a good thing in my opinion. One approach would be to increase the nicotine more slowly, increasing your tolerance gradually, but bear in mind that you will be increasing your level of nicotine addiction at the same time. The other approach is to play with flavors and see if any can help you be satisfied at the lower nic concentration.
Regardless, it will take a bit of determination to fully make the switch from smoking. However, when I started
vaping it did not totally satisfy me (at any nic level) and I smoked a few cigs a day. Gradually my subconscious mind came to understand that vaping did satisfy the nic cravings, and eventually I preferred vaping and now I go days without a smoke. I do still have a smoke now and then, but when I do, my lungs feel dirty and I go right back to vaping. But yes, it still requires some determination to stay off the cigs.
Edit: I don't know of anything you can add that will stop the hiccups, maybe someone does. You might also try slowing down on the high nic vape, or not inhaling quite so deeply. But hang in there, it will get easier over time. Don't equate relapsing a bit with total failure.