Some mothers have hyperlactation meaning an overabundance of breast milk. This causes milk to spray or leak out of the breast during breastfeeding which causes some babies to choke or gag on the first spray of milk. Here are some tips to prevent this:
Breastfeeding while lying on your back with your baby feeding on top of you will slow the supply of milk. Another possibility is holding your baby facing sitting up.
Another tip is expressing a bit of milk right before you breastfeed; this will get those few initial squirts out of the way.
Lastly, keep your baby feeding on one breast for at least 3 feedings. If the other breast feels full, relieve the pain by expressing a bit of milk from that breast
If hyperlactation does not settle within a few weeks, consult your physician as it could be a sign of hormonal imbalance.