the trigger on my milwaukee m18 drill driver feels sticky and sometimes doesn't work, can i fix it?

You could, but you really shouldn't. Opening it up for a DIY fix will void the warranty.

FIX: The safest route is to use the warranty. A sticky trigger that intermittently fails is a prime candidate for a defect in material or workmanship.

1. The tool has a five-year limited warranty.
2. Pack it up with a copy of your proof of purchase.
3. Send it freight prepaid and insured to a Milwaukee Service Center.

IF THAT DIDN'T WORK: If the examination finds the stickiness is due to exposure to paint, drywall dust, or other contaminants (misuse/lack of maintenance), it won't be covered.

HEADS UP: Even if warranty is denied, they can perform the repair for a cost. Either way, you need their authorized personnel to do the work to keep any future eligibility intact.