Neon sign lights up inconsistently

Hi teddysexton, I want to help you with your question, but I need more information from you. Can you please add details in the comment box?
so how old is it, ? 1year 10 , 100 years
1920 first true neon signs in USA>
i guess home toy sign?
or is it a modern sign (LED simulated NEON)
as in look ma' no real neon here?
I will answer you for true neon
there are 2 causes (I had one as a kid in 1955)

the neon gas is now bad inside, leaked out.
happens. on cheaper tubes
all have life span not too long
the best last a few decades.
the best tubes are heat processed when new for longer life. (RF induction)Just like Radio vacuum tubes, were, See my icon here this is huge RADIO TX tube with nitrogen leak purple.

next is bad transformer. weak.
not told at all how many tubes are there
1 or more and if more are all acting up?
just one color? or only neon orange.

a real display has real lable to tell who made it and a model. toys not so...much.... Hi teddysexton, I want to help you with your question, but I need more information from you. Can you please add details in the comment box? so how old is it, ? 1year 10 , 100 years 1920 first true neon signs in USA> i guess home toy sign? or is it a modern sign (LED simulated NEON) as in look ma' no real neon here? I will answer you for true neon there are 2 causes (I had one as a kid in 1955) the neon gas is now bad inside, leaked out. happens. on cheaper tubes all have life span not too long the best last a few decades. the best tubes are heat processed when new for longer life. (RF induction)Just like Radio vacuum tubes, were, See my icon here this is huge RADIO TX tube with nitrogen leak purple. next is bad transformer. weak. not told at all how many tubes are there 1 or more and if more are all acting up? just one color? or only neon orange. a real display has real lable to tell who made it and a model. toys not so...much....

"warm up"
is it cold where the sign is, not told
yes warm tubes start more easy.
but if the HV transformer is weak it fails
to ionize the neon// bingo that xfr bad.

some transformers are just flat 15k volts
others have starter the get it started using HV then drops to lower voltages but the length and diameter of the tube dictates needs.

life spans

lifespan of 10,000 to 25,000 hours

so 8 hours per night in BAR would be 6 years and dead. 17hours math
before ***** they act up, just like the huge fluorescent lamps do. "warm up" is it cold where the sign is, not told yes warm tubes start more easy. but if the HV transformer is weak it fails to ionize the neon// bingo that xfr bad. some transformers are just flat 15k volts others have starter the get it started using HV then drops to lower voltages but the length and diameter of the tube dictates needs. life spans lifespan of 10,000 to 25,000 hours so 8 hours per night in BAR would be 6 years and dead. 17hours math before ***** they act up, just like the huge fluorescent lamps do.