Same here today I swept the private key of an address with 0.005 btc(i ve sent that amount before) As soon as the transaction occured the btc automatically transferred to another address that i dont recognize Electrum wallet was downloaded from
https://electrum.org/#download 1LKrhFV52VMA9KKMv6pwM5k2Gp1PFnj6MA was the address that i swept the 0,005 btc
as others said it is most possible that you have some kind of malware on your computer that compromised your private key/seed or generated a wallet file as you installed Electrum to force you to think that is the wallet you created!
but there is a possibility that you downloaded a malicious file too
did you verify the signature of the file that you downloaded? maybe you have downloaded a file which was created by an attacker and placed for download.