Hi,
Intermittent makes it harder to find.
It could be any number of things, faulty trigger switch, loose wire etc.
The drill would have to be opened and tested as to what it may be, which may take a bit of time if it is intermittent
I cannot find a schematic for the drill but have found this [https://www.youtube.com/watch?v=OPsNI20fXC0|video] which shows the internal components (the voice over is in Polish but pictures are worth words)
Also found the [https://www.partshopdirect.co.uk/makita-dhp483-18v-brushless-cordless-combidrill-spare-parts-s18482/|parts diagram] which gives an idea of what parts are available etc.
If it is a component that is the problem and not wiring then if you search online using the manufacturer’s name and part number ''only'' in the search box of your web browser you will get results for suppliers that may suit you better, e.g. for the trigger switch, type in ''Makita 650689-0''
How old is the drill?
It seems that the manufacturer’s warranty on the drill is mostly 12 months but in some countries e.g. [https://www.makita.co.nz/warranty/|New Zealand], it can be 3 or 5 years and since it is a Lithium Ion tool (at least I think that it is) it is 3 years in the [https://www.makitatools.com/service/warranty|USA] as well. Check your location for the warranty on the drill to see if it still qualifies for a manufacturer’s warranty repair. Just a thought.