First thing you wanna check is in your panel box, you want to check your heat or your AC breaker. They should all easily be marked. Make sure you turn it to the off position, wait a second, turn it back on. If the breaker does keep tripping, you want to leave that off and call your service company. But if not, give it 3-5 minutes and see if the system comes back on.
Most systems have a digital thermostat. Most digital thermostats have batteries. You can just pop the cover off, check in the back and replace the batteries. Put it back on the wall. You’re gonna have a time delay on all thermostats so wait 3-5 minutes and see if the system comes back on. If not, you can move on to the next thing.
Next easy thing is the drain line could be backed up. You can flush it out with a vacuum, you can blow it out with a water hose. Either way, if your system does have a flow switch, once you flush the drain line out it should automatically reset itself. If it does, then you just wanna stay on maintenance, pour bleach in it once a month and service it every 6 months.
Another easy thing is checking your filter. Slide the filter out of the system, its right underneath the drain line. Pop it up, take a look, make sure the system is clear and the filter is clear and you can see through it. If not, replace it. You can also check underneath and see if there’s any ice. If you do see ice, change the filter and turn the fan to on and let it sit for a while and it should thaw that ice out. Turn it back on. If you still have the same problem, call your service company.