Prolonged political turmoil threatens to undermine the country's ambitions to join the euro zone in 2024 amid double-digit inflation and steep energy prices, and could lead to a softening of Sofia's stance on the Russian war in Ukraine.
Voting starts at 7 a.m. (0400 GMT) and ends at 8 p.m. (1700 GMT). Exit polls will be released after the ballots close, with first partial official results expected in the early hours of Monday.
Opinion polls suggest that up to eight political parties may enter the next parliament, with the centre-right GERB party of former long-serving premier Boyko Borissov, 63, leading with about 25%-26% of the vote.
Just as last year, Borissov, who has pledged to bring stability and be "stronger than the chaos", is widely expected to struggle to find coalition partners among his major rivals who accuse him of allowing graft to fester during his decade-long rule that ended in 2021.
The We Continue the Change (PP) party of reformist premier Kiril Petkov, whose coalition cabinet collapsed in June, is running second on 16-17% in opinion polls.
Failure to forge a functioning cabinet would leave the rule of the European Union and NATO-member state to a caretaker administration appointed by Russia-friendly President Rumen Radev.
NEW SNAP POLLS OR TECHNOCRAT CABINET
However, analysts say political parties, aware of economic risks from the war in Ukraine, a difficult winter ahead and voters' frustration of political instability, might put their differences behind them and opt for a technocrat government.
"Producing a government will be difficult and will require serious compromises," said Daniel Smilov, political analyst with Centre for Liberal Strategies.
Support for traditional parties like the ethnic Turkish MRF party, and Petkov's allies - the Socialists and the anti-graft Democratic Bulgaria - remains relatively unchanged since the last election in November.
Petkov's PP-led government took an unusually hawkish stance on Russia by Bulgaria, which has traditionally held friendly ties with Moscow. It refused, for example, to pay for Russian gas with roubles and has seen Gazprom cut off supplies.
One group that has seen more change is the pro-Russian ultra-nationalist Revival, which firmly opposes the adoption of the euro and wants to see Bulgaria out of NATO. It has more than doubled its support to about 11-14%, according to opinion polls.
Turnout is expected to be low with many voters angry over political infighting.
"I hope that all Bulgarians will come to their senses so ... we elect a stable government, but unfortunately the feeling I see do not give me promise," said 55-year-old lawyer Yulia Grozeva.
(Reporting by Tsvetelia Tsolova; Editing by Nick Macfie)
By Tsvetelia Tsolova