My dryer has been difficult to start lately especially if stopped mid cycle. The lights are all on but it won't start up. Today I only used it 2 times and it was very difficult to start after pressing many buttons plugging it in & unplugging it and pressing more buttons it came on. My dryer is not that old, it is still drying the clothes well. Any ideas?

You may be experiencing "Heat Retention" by stopping your dryer mid-cycle, which you should NOT ever have to do! If you have a minor vent restriction or if you open the dryer mid-cycle when the heat is on, this will cause a disruption in the airflow and rising temperatures can keep the dryer from restarting until it has been cooled long enough.
Check your vent all the way to the outside for restrictions/obstructions every 6 months. Clean your lint filter after each load and DO NOT stop the dryer mid-cycle!
Note: Stopping the dryer mid-cycle can also cause severe burns and even melt polyester fibers.