The starting problem is probably because the car was not used for such a long time. If battery voltage is too low, the electronics play .
Use a multimeter an check battery voltage, cranking voltage at lowest point and charging voltage of the alternator.
There are certain points which should be kept as minimum. Any gas/fuel station can tell you.
If you want to do it (here are my test procedures) from Patrick copied
Find a digital multimeter (a useable one can be had for $15) and stick the probe into the cigarette lighter socket in the center console.
The following are the detail figures I use for my own evaluation:
With key out of ignition switch, should see 12.4V or above. 12.0 V is getting low.
With key inserted and turned to position 2 (don't start car), should see 12.0V or more. 11.6V would be too low.
Crank car, catch the lowest voltage reading during that couple of seconds. Should see 10.0V or above. 9.5V would be marginal.
The above just consider the health of battery itself.
Car running at 1500 RPM or more, should see 13.7 to 14.3V, 13.6V or below means the charging system is weak.
Hazard lights: most probbably the crash alarm relay in the fuse box right of the check control module. Brown colour, replacement cost roughly $ 50.
Had same prob before for half a year and learned it the hard way by exchanging /checking may parts over months. Sometimes I heard also the GM is the problem.
PS: if you use the search engine, all is already covered on these subjects and much more info there.