If so, for how long for 30 ml?
This question has been asked many times and I've read them all. The biggest thing I got out of it was to be made aware that unlike water PG/VG warms up much faster and gets far hotter then water. So you need to be aware of this and handle the warmed juice very carefully so not to get burned. One individual warmed it in the microwave to long and as he opened up the microwave door the bottle exploded scalding him very badly. Many others have also reported exploding bottles.
I myself have warmed juice/pg/vg/nic in the microwave and misjudged the temperature and got just a few drops on my skin and it burned like heck. So if this is the route you want to go use extreme caution when handling this juice.
When I take my base out of the refrigerator I some times use a microwave to warm it to room temperature when I'm in a hurry. I have learned to do short bursts of a few seconds checking it each time until it gets to room temperature.
So in general my opinion of using a microwave is it should be avoided but if you are dead set on using it be very careful.
I do not recommend using a microwave at all as a steeping method due to the high risk of scalding yourself..
Safety should always come first.