Most often, if you have been asked to present something, then it is because you know more about the subject than anyone else in the audience.
Gain confidence from that fact.
I find, that running through my presentation in my head (a speeded up version) shortly before presenting on a new subject, helps me feel more in control.
Deep Breathing techniques, centering yourself before you begin to speak will all help.
However, you have also mentioned that this was not a problem for you before. Will it be possible for you to do some personal introspection as to when this changed and thus figure out what triggered it.
Once you know the source or trigger for your nervousness / anxiety – it would be easier to suggest personalised solutions

Ha.. Ha… everyone gets the heebeegeebees before presenting in front of an audience. It helps to know your material well, which you have mentioned that you do.
Maybe spice up your presentations a bit more, raise the energy of the audience and that may help you shine brighter. Think of how you could get the audience to lean in, maybe a short quiz , a role play, build a story with the audience. Basically something creative and fun, something you can’t completely control… so you are engrossed in the session and forget your inhibitions. Dive into the deep end.. 😊

Confidence is the key! Yes presenting in front of a large crowd is nerve wrecking. Everyone feels nervous and that’s absolutely normal.it only depends on the way you handle it firstly be prepared, thoroughly practice your topic, cause until and unless you know your topic well there are chances of you stuttering or getting stuck. practice your presentation prior to the day it has to be presented.
Check all the necessary materials required to ensure there is no hinderance.
Stay hydrated, breathe and smile
you are good to go
All the best 😉