Hey I am facing same kind of issues I have Dell Inspiron 15 3521 I had issue in my power segment on my motherboard (as repair shop guy told because few drop of water was felt) the issue is when booting my laptop is turning on but no dell logo appears most of time only black screen but after few times of on/off it starts(boot) normally i have tried changing CMOS battery and RAM yes my boot options are working few time while black screen then also it boots up normally and also no issue while rebooting or sleep. Please reply if you have any solution or suggestion.