What Microwave are you using?

I'd say first just make sure that your electric system/inverter is able to handle whatever wattage you choose (I went with a $140 cheapo 900w B&D, but it did rattle a bit until I put a small piece of foam between it and the enclosure). Next, some drivers seem to like the microwave/convection oven combinations, but I decided I just didn't want to deal any smoke problems? Lastly, I'd bet there might be some good information available online from the RV community. Like you say, I wouldn't be surprised if there are some units available actually made for use in vehicles.

Edit: I did remember the RV appliances company 'Dometic', and sure enough they do make ovens for vehicles - Enjoy fast heating power, browning, & crisping with an RV convection microwave from Camping World. Available now!

 

I had a 1500 watt inverter in my Kenworth and it would only run my 700 watt Walmart cheap microwave when it felt like it. So I went to the Kenworth dealer and bought a 600 watt Sharp Half Pint microwave and it worked perfectly. In 2013 when I got my new Peterbilt, I put a 2000 watt Tundra inverter in it and I’m still using the Sharp Half Pint. I’m going to put a 700 watt Walmart cheap microwave in it if the Sharp ever craps out as I believe this 2000 watt will run it. I never run my microwave nor coffee pot unless the engine is running.

ETA: Looking around online, it doesn’t look like they make my Sharp unit anymore. Found some used refurbished ones for more $ than I paid for mine.
WORKING Sharp Half Pint Carousel Microwave Black Gray Compact RV R120-DK Mini | eBay

 

Cables and circuit breaker make a difference too, my 3000 watt pure sin will run it but even with 2 awg welding cable trips the breaker of run for more then 30 seconds, yet my HF 2000 watt gen runs it just fine

I have a 700w Walmart special

 

I use a 3000 watt inverter, and the manufacture specifies 4/0 awg cable in order obtain full wattage. 4/0 would be similar to the size cables running from the starter to the battery.

 

I use a cheap Walmart microwave. Works perfectly fine. I just picked one that’s lower wattage. Make sure your inverter can handle it. I precook and freeze most of my meals on my day off, I have a compact small freezer I keep on the truck as well. What a life changer being out on the road being able to eat healthy home-cooked meals. And it’s fast too. I pop one out of the freezer into the microwave and four minutes later I’m eating a home-cooked meal.

 

I just have a cheapo one but I cut a piece of styrofoam to set underneath the turntable plate so it won’t rattle and drive me nuts.

 

I've always wondered that too. I'm afraid to mess with mine. The rattle doesn't bother me but I do have to put the plate back on the spindle every day or two.

2500 PSW inverter running a Walmart cheapo (700w?) for about 4 years now, no problems.