Now it has 4 red blinking lights on after the tv turns on

Https://docs.sony.com/release/KDFE42-50A10.pdf

all three lights are on because

1 the lamp needs changed
2 the overheat is running hot because the fans and heatsinks are cloged with dust
3 its shut down because the lamp is old failed and overheating

above is the link to the manual study it and youll see...

clean it out fully
drop the back off demount some pcb and fans etc
and vaccume out carefully and change the bulb

basically a good service needs doing
if your not in the mood and use ebay to get a new bulb cheep {prob one without the holder}
then take it too a tech

if you take it get the cheep bulb option first and have him fit it
safe you getting ripped off for parts cost...

its just the bulb and fan units

so dont panic

the projection screen might need a clean with IPA and the reflector panel cleaned also
depends what the TV setup is not familiar with this model fully

much as a much in this type

all thee lights is common to bulb going meltdown... soon

so change it out and clean all is the rule here

happy crimbo...
anyway

sim